ci: Auto-approve and merge dependabot PRs

[terrytangyuan]

Signed-off-by: terrytangyuan terrytangyuan@gmail.com

[terrytangyuan]

This will auto-merge dependabot PRs (when CI builds pass) but one issue is that CI will pass anyway if there's no review requested.

Should we remove review_requested from ci.yml? I remember it's only used to save some build time on GA. We should have enough build time now since the project is open sourced.

[gaocegege]

Should we remove review_requested from ci.yml? I remember it's only used to save some build time on GA. We should have enough build time now since the project is open sourced.

Sure, we can remove it.