make repository mirror alert container scrollable
Created by: BolajiOlajide
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Test plan
When the error from a repository mirroring action is very large, we end up with a state in which the error is spilled over a large portion of the browser window.
This PR adds a max-height to the repository alert container and makes it scrollable when the error is large.
App preview:
Check out the client app preview documentation to learn more.