Investigate how to de-duplicate dependabot / renovatebot PRs

[alicejli]

Currently, both dependabot and renovatebot are enabled on this repo.
This results in duplicate dependency updates to the main (i.e. 5.x) branch of this repo.
Example:

• (dependabot): deps: bump com.google.truth:truth from 1.4.0 to 1.4.1 #2617
• (renovatebot): chore(deps): update dependency com.google.truth:truth to v1.4.2 #2611

Furthermore, because dependabot updates dependecies via the repo itself, whereas renovatebot updates dependencies via a fork of the repo, when one of the PRs is merged, the other doesn't recognize it and doesn't automatically rebase/close, which can result in confusion.

It would help reduce the number of PRs in the repo if we can remove duplicate dependency updates.

[alicejli]

oops didn't realize @suztomo had already made an internal bug for this. Closing - follow along at b/326598983