Update dotnet-build-test.yml to 'main' branch after merge

Author: crpietschmann

.github/workflows/dotnet-build-test.yml

@@ -2,9 +2,9 @@ name: .NET
 
 on:
   push:
-    branches: [ "feature/begin-core" ]
+    branches: [ "main" ]
   pull_request:
-    branches: [ "feature/begin-core" ]
+    branches: [ "main" ]
   schedule:
     - cron: '0 0 * * *'