Show confirmation after updating project git hooks

Zendesk: https://gitlab.zendesk.com/agent/tickets/16033

If I edit a project's git hooks and hit 'save' I see no confirmation in the browser ('git hooks settings saved'). It would be nice to have that.

@vsizov milestone?

Milestone changed to 8.7

assigned 8.7

Milestone changed to 8.8

Milestone changed to %8.9

Reassigned to @patricio

mentioned in merge request !475 (merged)

Status changed to closed by merge request !475 (merged)

mentioned in commit 75157724

mentioned in commit 7b612762

Mentioned in commit 75157724

Mentioned in commit 7b612762

mentioned in commit 5c59b053