Update documentation to indicate activity size limit across all SDKs

docs/develop/go/core-application.mdx

@@ -492,7 +492,7 @@ func (a *YourActivityObject) YourActivityDefinition(ctx context.Context, param Y
 
 All data returned from an Activity must be serializable.
 
-There is no explicit limit to the amount of data that can be returned by an Activity, but keep in mind that all return values are recorded in a [Workflow Execution Event History](/workflow-execution/event#event-history).
+Activity return values are subject to payload size limits in Temporal. The default payload size limit is 2MB, and there is a hard limit of 4MB for any gRPC message size in the Event History transaction ([see Cloud limits here](https://docs.temporal.io/cloud/limits#per-message-grpc-limit)). Keep in mind that all return values are recorded in a [Workflow Execution Event History](/workflow-execution/event#event-history).
 
 A Go-based Activity Definition can return either just an `error` or a `customValue, error` combination (same as a Workflow Definition).
 You may wish to use a `struct` type to hold all custom values, just keep in mind they must all be serializable.

docs/develop/java/core-application.mdx

@@ -378,7 +378,7 @@ For more details, see [Dynamic Activity Reference](https://www.javadoc.io/doc/io
 
 All data returned from an Activity must be serializable.
 
-There is no explicit limit to the amount of data that can be returned by an Activity, but keep in mind that all return values are recorded in a [Workflow Execution Event History](/workflow-execution/event#event-history).
+Activity return values are subject to payload size limits in Temporal. The default payload size limit is 2MB, and there is a hard limit of 4MB for any gRPC message size in the Event History transaction ([see Cloud limits here](https://docs.temporal.io/cloud/limits#per-message-grpc-limit)). Keep in mind that all return values are recorded in a [Workflow Execution Event History](/workflow-execution/event#event-history).
 
 Activity return values must be serializable and deserializable by the provided [`DataConverter`](https://www.javadoc.io/static/io.temporal/temporal-sdk/1.17.0/io/temporal/common/converter/DataConverter.html).
 

docs/develop/php/core-application.mdx

@@ -194,7 +194,7 @@ The default implementation uses a JSON serializer, but an alternative implementa
 
 All data returned from an Activity must be serializable.
 
-There is no explicit limit to the amount of data that can be returned by an Activity, but keep in mind that all return values are recorded in a [Workflow Execution Event History](/workflow-execution/event#event-history).
+Activity return values are subject to payload size limits in Temporal. The default payload size limit is 2MB, and there is a hard limit of 4MB for any gRPC message size in the Event History transaction ([see Cloud limits here](https://docs.temporal.io/cloud/limits#per-message-grpc-limit)). Keep in mind that all return values are recorded in a [Workflow Execution Event History](/workflow-execution/event#event-history).
 
 Return values must be serializable to a byte array using the provided [DataConverter](https://github.com/temporalio/sdk-php/blob/master/src/DataConverter/DataConverterInterface.php) interface.
 The default implementation uses a JSON serializer, but an alternative implementation can be easily configured.

docs/develop/python/core-application.mdx

@@ -285,7 +285,7 @@ async def your_activity(input: YourParams) -> str:
 
 All data returned from an Activity must be serializable.
 
-There is no explicit limit to the amount of data that can be returned by an Activity, but keep in mind that all return values are recorded in a [Workflow Execution Event History](/workflow-execution/event#event-history).
+Activity return values are subject to payload size limits in Temporal. The default payload size limit is 2MB, and there is a hard limit of 4MB for any gRPC message size in the Event History transaction ([see Cloud limits here](https://docs.temporal.io/cloud/limits#per-message-grpc-limit)). Keep in mind that all return values are recorded in a [Workflow Execution Event History](/workflow-execution/event#event-history).
 
 An Activity Execution can return inputs and other Activity values.
 

docs/develop/typescript/core-application.mdx

@@ -504,7 +504,7 @@ export async function greet(name: string): Promise<string> {
 
 All data returned from an Activity must be serializable.
 
-There is no explicit limit to the amount of data that can be returned by an Activity, but keep in mind that all return values are recorded in a [Workflow Execution Event History](/workflow-execution/event#event-history).
+Activity return values are subject to payload size limits in Temporal. The default payload size limit is 2MB, and there is a hard limit of 4MB for any gRPC message size in the Event History transaction ([see Cloud limits here](https://docs.temporal.io/cloud/limits#per-message-grpc-limit)). Keep in mind that all return values are recorded in a [Workflow Execution Event History](/workflow-execution/event#event-history).
 
 In TypeScript, the return value is always a Promise.