ci: bump nightly to 2024-09-15 #722

Job	Run time
cross (i686-unknown-linux-gnu)	26s
minrust	49s
cross (armv7-unknown-linux-gnueabihf)	25s
cross (powerpc-unknown-linux-gnu)	26s
miri	13m 29s
cross (powerpc64-unknown-linux-gnu)	33s
nightly	1m 5s
loom	22s
rustfmt	6s
cross (wasm32-unknown-unknown)	8s
stable (ubuntu-latest)	2m 23s
stable (macos-latest)	1m 31s
tsan	1m 24s
stable (windows-latest)	2m 56s
Publish Documentation	0s
	26m 3s

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