[Feature] Handle dependabot alerts on a regular basis

[ashwani2k]

Feature (What you would like to be added):
Manage the dependabot alerts in a structured way with each release by planning updates ahead or close the PR if they don't add value.

Motivation (Why is this needed?):
The repos was configured with dependabot which should help in automatic managing of upstream dependencies.
Currently these are ignored and are closed automatically when dependabot raises fresh PR for newer versions.

You can check the current open ones here -- https://github.com/gardener/etcd-backup-restore/pulls?q=is%3Apr+is%3Aopen+bump

Approach/Hint to the implement solution (optional):

• Remove dependabot as currently its just ignored
• Create a standard process which can include these PR's as part of milestones planned for the etcd-br release.