chore: Fixing renovate config

[ddixit14]

All configuration as per https://docs.renovatebot.com/configuration-options/.

Might fix #2067
(Will re-open the issue if it gets closed and this fix doesn't work).

[sonarqubecloud]

[gapic-generator-java-root] Kudos, SonarCloud Quality Gate passed!   

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[sonarqubecloud]

[java_showcase_integration_tests] Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[sonarqubecloud]

[java_showcase_unit_tests] Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[blakeli0]

Can you briefly explain why it stopped working previously? And how did you test this fix? Or it was not tested?

[ddixit14]

Can you briefly explain why it stopped working previously? And how did you test this fix? Or it was not tested?

We temporarily stopped it for sometime post the migration to monorepo. Then opened it back. It should have worked ideally, I don't know the reason why it didn't. As first steps, I made sure that the configuration is as per the documentation, hence this PR.
This fix is not tested yet. Once this is merged, then we'll see if we are getting the updates or not. If not, then I will dig further.