Add main to YAML files (#23143)

Author: gewarren

.github/workflows/build-validation.yml

@@ -19,7 +19,7 @@ on:
       - "**.sln"
       - "**global.json"
       - "**snippets.5000.json"
-    branches: [ master ]
+    branches: [ master, main ]
 
 env:
   DOTNET_INSTALLER_CHANNEL: 'release/5.0.1xx'

.github/workflows/version-sweep.yml

@@ -4,7 +4,7 @@ name: 'target supported version'
 
 # Controls when the action will run. 
 on:
-  # Triggers the workflow on push or pull request events but only for the master branch
+  # Triggers the workflow on push or pull request events but only for the default branch
   schedule:
   - cron: '0 0 1 * *'
   workflow_dispatch: