Bump slab to v0.4.7 #790

Job	Run time
fmt	6s
clippy	17s
msrv (ubuntu-latest)	34s
cross (ubuntu-latest)	1m 25s
msrv (windows-latest)	1m 1s
security_audit	1s
cross (macos-latest)	1m 4s
test (ubuntu-latest, nightly)	39s
test (ubuntu-latest, beta)	37s
windows_gnu (nightly, x86_64-pc-windows-gnu)	1m 34s
test (ubuntu-latest, stable)	33s
test (windows-latest, nightly)	1m 14s
test (windows-latest, beta)	1m 10s
test (windows-latest, stable)	1m 33s
test (macos-latest, nightly)	44s
test (macos-latest, beta)	41s
test (macos-latest, stable)	37s
	13m 50s

Provide feedback