deps: update googleapis/java-cloud-bom digest to 47c5dbc (#2974)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| googleapis/java-cloud-bom | action | digest | `17cc5ec` -> `47c5dbc` |

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.github/workflows/ci.yaml

@@ -327,7 +327,7 @@ jobs:
       run: |
         mvn install -B -ntp -DskipTests -Dclirr.skip -Dcheckstyle.skip
     - name: Validate gapic-generator-java-bom
-      uses: googleapis/java-cloud-bom/tests/validate-bom@17cc5ecf3730d0671f233c0879dc654337b38cba
+      uses: googleapis/java-cloud-bom/tests/validate-bom@47c5dbc0b2c9a7d120cc12eb3650db89ab5b894f
       with:
         bom-path: gapic-generator-java-bom/pom.xml