chore: fix renovate bot configs for java-shared-config updates

[mpeddada1]

Fixes #2511. Verified with mpeddada1/forking-renovate-repro#15

The Dependency Dashboard logs were shows the status of java-shared-config as being skipReason:disabled. Explicitly setting enabled to true resolves this issue.

{
            "datasource": "maven",
            "depName": "com.google.cloud:google-cloud-shared-config",
            "currentValue": "1.7.1",
            "fileReplacePosition": 873,
            "registryUrls": [
              "https://repo.maven.apache.org/maven2",
              "https://maven-central.storage-download.googleapis.com/maven2",
              "https://repo1.maven.org/maven2",
              "https://maven-central.storage-download.googleapis.com/maven2/"
            ],
            "depType": "parent-root",
            "updates": [],
            "packageName": "com.google.cloud:google-cloud-shared-config",
            "skipReason": "disabled"
          },

[sonarcloud]

Quality Gate passed for 'gapic-generator-java-root'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[sonarcloud]

Quality Gate passed for 'java_showcase_integration_tests'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud