Bump buildpacks/gradle/test-apps/heroku-gradle-getting-started (#765)

Bumps [buildpacks/gradle/test-apps/heroku-gradle-getting-started](https://github.com/heroku/gradle-getting-started) from `506f247` to `3b16adc`.
- [Commits](heroku/gradle-getting-started@506f247...3b16adc)

---
updated-dependencies:
- dependency-name: buildpacks/gradle/test-apps/heroku-gradle-getting-started
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>