Replace Gradle update checker

[TheLastProject]

The current update checker, https://github.com/obfusk/gradle-update-action, has sadly stopped working and is no longer maintained.

Need to replace it with the official upstream Gradle version update checker (or dependabot, if that supports it)

[JessieG-TY]

This will scan build.gradle.kts and every module, automatically detects if Gradle is out of date every week.

version: 2
updates: 
  - package-ecosystem: "gradle"
    directory: "/"
    schedule:
      interval: "weekly" 
    open-pull-requests-limit: 5
    commit-message:
      prefix: "deps" 

[TheLastProject]

As stated in #2529, we already have dependabot running for years, but it only seems to update dependencies, not gradle itself, which is why we also had https://github.com/CatimaLoyalty/Android/blob/e297620ea24b51ebfb739aad2b00edf3f9905ff1/.github/workflows/gradle-update.yml for years to make PRs like #2474 but which stopped working and is no longer maintained.

I'm pretty sure the Gradle team has some official Github Action for this, which is probably the safest way.