Update which requirement from ^4.0 to ^7.0 #2124

Job	Run time
Test wasm (wasm32-unknown-unknown)	16s
Test CUDA support	37s
Test build-std (aarch64-tvos)	2m 1s
MSRV (ubuntu-latest)	1m 30s
Test build-std (aarch64-tvos-sim)	1m 54s
Clippy	25s
MSRV (windows-latest)	2m 4s
Test build-std (x86_64-tvos)	2m 30s
Rustfmt	12s
MSRV (macos-latest)	1m 45s
semver-checks	2m 28s
Test wasm32-wasip1-thread	34s
Test (stable)	1m 54s
Test (beta)	1m 41s
Test (nightly)	2m 1s
Test (linux32)	2m 6s
Test (macos)	2m 16s
Test (aarch64-macos)	1m 44s
Test (aarch64-ios)	1m 31s
Test (win32)	2m 2s
Test (win64)	2m 0s
Test (mingw32)	1m 54s
Test (mingw64)	2m 0s
Test (windows-2019)	2m 4s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	2m 0s
Test (windows-clang, windows-2019, stable, x86_64-pc-windows-msvc, clang, clang++)	2m 2s
Test (windows-clang-cl, windows-2019, stable, x86_64-pc-windows-msvc, clang-cl, clang-cl)	2m 1s
	45m 32s

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