skip workflow for non release branches on push (opensearch-project#5964)

Signed-off-by: Ashwin P Chandran <[email protected]>

.github/workflows/build_and_test_workflow.yml

@@ -6,7 +6,7 @@ name: Build and test
 # trigger on every commit push and PR for all branches except pushes for backport branches
 on:
   push:
-    branches: ['**', '!backport/**']
+    branches: ['main', '[0-9].x', '[0-9].[0=9]+'] # Run the functional test on push for only release branches
     paths-ignore:
       - '**/*.md'
       - 'docs/**'