Bump actions/checkout from 2 to 4 #140

Job	Run time
Minimum supported rust version	6m 23s
Code quality	54s
ubuntu-20.04 (arm-unknown-linux-gnueabihf)	4m 52s
ubuntu-20.04 (arm-unknown-linux-musleabihf)	3m 39s
ubuntu-20.04 (aarch64-unknown-linux-gnu)	3m 33s
ubuntu-20.04 (i686-unknown-linux-gnu)	2m 50s
ubuntu-20.04 (i686-unknown-linux-musl)	4m 13s
ubuntu-20.04 (x86_64-unknown-linux-gnu)	2m 59s
ubuntu-20.04 (x86_64-unknown-linux-musl)	3m 9s
macos-latest (x86_64-apple-darwin)	3m 5s
windows-2019 (i686-pc-windows-msvc)	5m 8s
windows-2019 (x86_64-pc-windows-gnu)	7m 57s
windows-2019 (x86_64-pc-windows-msvc)	4m 58s
Publish to Winget	0s
	53m 40s

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