remove unused links and update broken links (#420)

Signed-off-by: Sean Li <[email protected]>

CONTRIBUTING.md

@@ -47,7 +47,7 @@ Looking at the existing issues is a great way to find something to contribute on
 
 ## Developer Certificate of Origin
 
-OpenSearch is an open source product released under the Apache 2.0 license (see either [the Apache site](https://www.apache.org/licenses/LICENSE-2.0) or the [LICENSE.txt file](./LICENSE.txt)). The Apache 2.0 license allows you to freely use, modify, distribute, and sell your own products that include Apache 2.0 licensed software.
+OpenSearch is an open source product released under the Apache 2.0 license (see either [the Apache site](https://www.apache.org/licenses/LICENSE-2.0) or the [LICENSE file](./LICENSE)). The Apache 2.0 license allows you to freely use, modify, distribute, and sell your own products that include Apache 2.0 licensed software.
 
 We respect intellectual property rights of others and we want to make sure all incoming contributions are correctly attributed and licensed. A Developer Certificate of Origin (DCO) is a lightweight mechanism to do that.
 

DEVELOPER_GUIDE.md

@@ -28,10 +28,6 @@ The output file : `./build/searchRelevanceDashboards-?.?.?.zip` (`?.?.?` stands
 
 Cd back to `OpenSearch-Dashboards` directory and run `yarn start` to start OpenSearch Dashboards including this plugin. OpenSearch Dashboards will be available on `localhost:5601`.
 
-### Run Docker
-
-Run `docker-compose up -d` after changing the [Dockerfile](Dockerfile) as described in this [tutorial](Using-Docker.md)
-
 ### Submitting Changes
 
 See [CONTRIBUTING](CONTRIBUTING.md).