Bump git2 from 0.17.2 to 0.18.1 #6806

Job	Run time
build-linux-arm (nightly)	8m 35s
Lints	1m 5s
build-linux-arm (stable)	8m 6s
build-linux-musl (nightly)	4m 59s
build-linux-arm (1.65)	9m 3s
build (ubuntu-latest, nightly)	2m 3s
build-linux-musl (stable)	4m 31s
build (ubuntu-latest, stable)	1m 50s
build-linux-musl (1.65)	4m 40s
build (ubuntu-latest, 1.65)	1m 47s
Changelog Test	7s
build (macos-latest, nightly)	4m 2s
Security audit	10s
build (macos-latest, stable)	3m 12s
udeps	2m 42s
build (macos-latest, 1.65)	3m 48s
build (windows-latest, nightly)	4m 46s
build (windows-latest, stable)	6m 25s
build (windows-latest, 1.65)	4m 43s
	1h 16m 34s

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