build

docs: mention `git pack-refs` for co-located repos #6891

Job	Run time
build (ubuntu-latest)	7m 47s
cargo-deny (advisories)	32s
build (macos-13)	4m 10s
cargo-deny (bans licenses sources)	33s
build (windows-latest)	8m 34s
build (ubuntu-latest, --all-features)	7m 12s
Check protos	38s
Clippy check	2m 49s
Check formatting	16s
Check that MkDocs can build the docs	23s
	32m 54s

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