remove git2 from cargo-smart-release #2987

Job	Run time
lint	4m 0s
cargo-deny (advisories)	37s
cargo-deny (bans licenses sources)	40s
installation (win-msvc)	13m 49s
installation (win-gnu)	12m 33s
installation (win32-msvc)	14m 7s
pure-rust-build	4m 10s
test	27m 45s
test-fast (windows-latest)	14m 10s
test-fast (macos-latest)	7m 38s
WebAssembly (wasm32-unknown-unknown)	1m 23s
WebAssembly (wasm32-wasi)	56s
test-32bit	57s
	1h 42m 45s

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