ci: skip enfocer when preparing the gapic-libraries-bom check (#11234)

Running the enforcer rule in another check than 'enforcer' causes
irrelevant failures in the check. The enforcer check when installing
the modules is not necessary.

Author: suztomo

.github/workflows/ci.yaml

@@ -110,7 +110,7 @@ jobs:
         cache: maven
     - name: Install Maven modules to local Maven repository
       run: |
-        mvn install -B -ntp  -T 1C -DskipTests -Dclirr.skip -Dcheckstyle.skip
+        mvn install -B -ntp  -T 1C -DskipTests -Dclirr.skip -Dcheckstyle.skip -Denforcer.skip
     - name: Validate gapic-libraries-bom
       uses: googleapis/java-cloud-bom/tests/[email protected]
       with: