cargo: point `repository` metadata to clonable URLs #501

Job	Run time
build (1.60.0, thumbv7em-none-eabi)	1m 7s
test (i686-unknown-linux-gnu, ubuntu-latest, 1.60.0, sudo apt update && sudo apt install gcc-mult...	27s
build (1.60.0, wasm32-unknown-unknown)	1m 11s
cross (aarch64-unknown-linux-gnu, 1.60.0)	42s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.60.0)	14s
build (stable, thumbv7em-none-eabi)	8s
cross (aarch64-unknown-linux-gnu, stable)	38s
test (x86_64-pc-windows-msvc, windows-latest, 1.60.0)	1m 36s
build (stable, wasm32-unknown-unknown)	22s
cross (powerpc-unknown-linux-gnu, 1.60.0)	40s
test (x86_64-apple-darwin, macos-latest, 1.60.0)	1m 41s
cross (powerpc-unknown-linux-gnu, stable)	30s
minimal-versions / minimal-versions	18s
	9m 34s

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