Make build.yml triggers include all release_* branches

Make the on/push and on/pull_request triggers list release_* branches
instead of only release_4* so that validation builds are triggered for
all release branches when changes are being backported.

.github/workflows/build.yml

@@ -4,12 +4,12 @@ on:
   push:
     branches:
       - develop
-      - release_4*
+      - 'release_*'
 
   pull_request:
     branches: 
     - develop
-    - release_4*
+    - 'release_*'
 
 jobs:
   build: