Use new PR workflow

Author: ryanjbaxter

.github/workflows/ci-maven-main.yml

@@ -0,0 +1,9 @@
+name: PR
+
+on:
+    pull_request:
+        branches: [ 3.3.x ]
+
+jobs:
+    build:
+        uses: spring-cloud/spring-cloud-github-actions/.github/workflows/pr.yml@main