Ref the branch ubi9 for image test

Author: sswguo

.github/workflows/merge-build.yml

@@ -61,6 +61,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: Commonjava/commonjava-images
+          ref: ubi9
           path: commonjava-images
 
       - name: Locate artifacts