generation config should declare monorepo

Author: chingor13

.github/workflows/sdk-platform-java-ci.yaml

@@ -361,7 +361,7 @@ jobs:
         run: .kokoro/build.sh
         env:
           BUILD_SUBDIR: sdk-platform-java
-          JOB_TYPE: test      
+          JOB_TYPE: install
       - name: Showcase golden tests
         working-directory: sdk-platform-java/java-showcase
         run: |

generation_config.yaml

@@ -1,6 +1,7 @@
 gapic_generator_version: 2.70.0
 googleapis_commitish: 62e4ecb2f4390728990514fea14aad0431881a52
 libraries_bom_version: 26.79.0
+is_monorepo: true
 libraries:
 - api_shortname: accessapproval
   name_pretty: Access Approval