Update branch name in CI (#2087)

.github/workflows/ci.yaml

@@ -1,9 +1,9 @@
 name: CI
 on:
   push:
-    branches: [main]
+    branches: ["release/1.x"]
   pull_request:
-    branches: [main]
+    branches: ["release/1.x"]
 jobs:
   preflight:
     name: License Header and Formatting Checks