Replace fork of Context Menu Plugin with Upstream

[namanlp]

Hi there!

(This PR is copy of https://github.com/gitbutlerapp/gitbutler/pull/2581, but is cleaner and cargo.lock is also updated )

So, Tauri Plugin Context Menu do have Linux Support now 🎉

Hence, the fork of it can be replaced with the upstream. I have not tested it yet though, and hence, making it as a draft PR for now.

Also, now looking at the source, I am wondering why tauri-plugins are explicitly fetched from git? This may cause issue because they might use unreleased version.

Thank You