Update verify-staged-artifacts.yml for SI 6.4.x

Signed-off-by: Soby Chacko <[email protected]>

Author: sobychacko

.github/workflows/verify-staged-artifacts.yml

@@ -23,6 +23,7 @@ jobs:
         with:
           repository: spring-projects/spring-integration
           show-progress: false
+          ref: 6.4.x
 
       - name: Set up Gradle
         uses: spring-io/spring-gradle-build-action@v2
@@ -52,4 +53,4 @@ jobs:
         with:
           name: test-results
           path: '**/target/surefire-reports/**/*.*'
-          retention-days: 1
+          retention-days: 1