git sync: unhide `jj git sync` #16541

Job	Run time
Build jj-lib without Git support	43s
cargo-deny (advisories)	25s
Check protos	44s
build (ubuntu-latest)	1m 36s
cargo-deny (bans licenses sources)	25s
Clippy check	2m 24s
build (macos-13)	2m 48s
Check that MkDocs can build the docs	12s
build (macos-14)	1m 38s
Check that MkDocs can build the docs with latest Python and uv	11s
Check formatting	18s
build (windows-latest)	4m 0s
build (ubuntu-latest, --all-features)	2m 30s
	17m 54s

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