build

docs: mention that that Rust 1.76 is required to install from source #15210

Job	Run time
build (ubuntu-latest)	4m 40s
build (macos-13)	5m 31s
Check protos	31s
build (macos-14)	3m 38s
build (windows-latest)	12m 25s
Build jj-lib without Git support	43s
cargo-deny (advisories)	22s
build (ubuntu-latest, --all-features)	5m 32s
Clippy check	2m 39s
cargo-deny (bans licenses sources)	22s
Check that MkDocs can build the docs	22s
Check that MkDocs can build the docs with Poetry 1.8	22s
Check formatting	18s
	37m 25s

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