CI: Remove `musl-tools` install step #436

Job	Run time
Get declared MSRV from Cargo.toml	8s
Check code formatting (1.74.0)	12s
Test on each target (android-aarch64, 1.74.0)	4m 53s
Check code formatting (stable)	13s
Test on each target (android-aarch64, stable)	4m 38s
Check code formatting (nightly)	12s
Test on each target (android-aarch64, nightly)	4m 47s
Test on each target (linux-x64-gnu, 1.74.0)	2m 24s
Test on each target (linux-x64-gnu, stable)	2m 19s
Test on each target (linux-x64-gnu, nightly)	2m 18s
Test on each target (linux-x64-musl, 1.74.0)	2m 32s
Test on each target (linux-x64-musl, stable)	2m 26s
Test on each target (linux-x64-musl, nightly)	2m 20s
Test on each target (macos-x64, 1.74.0)	3m 24s
Test on each target (macos-x64, stable)	2m 9s
Test on each target (macos-x64, nightly)	4m 45s
Test on each target (windows-x64-msvc, 1.74.0)	5m 14s
Test on each target (windows-x64-msvc, stable)	4m 59s
Test on each target (windows-x64-msvc, nightly)	4m 51s
	54m 44s

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