When `force` is set to `true` and `start_branch` is set, the
branch will be ovewritten with the new commit based on the
`HEAD` of the `start_branch`.
This commit includes changes to update the `gitaly-proto` gem.
If `source_branch` option is passed, and target branch cannot be found,
`Repository#update_branch_with_hooks` would try to create a new branch
from `source_branch`.
This way, we could make changes in the new branch while only firing
the hooks once for the changes. Previously, we can only create a new
branch first then make changes to the new branch, firing hooks twice.
This behaviour is bad for CI.
Fixes#7237
