Update build_and_test.yml to match r2.8 and r2.8.1

Author: bhavya01

.github/workflows/build_and_test.yml

@@ -3,11 +3,11 @@ on:
   pull_request:
     branches:
       - master
-      - r[0-9]+.[0-9]+
+      - r[0-9]+.[0-9]+(\.[0-9]+)?
   push:
     branches:
       - master
-      - r[0-9]+.[0-9]+
+      - r[0-9]+.[0-9]+(\.[0-9]+)?
   workflow_dispatch:
 
 concurrency: