ci: Pin no-std test to nightly-2023-08-05 #245

Job	Run time
test (nightly, aarch64-unknown-linux-gnu)	2m 9s
test (nightly, mips64-unknown-linux-gnuabi64)	4m 36s
no-std (1.64)	4m 42s
no-std (stable)	3m 26s
no-std (beta)	3m 14s
no-std (nightly-2023-08-05)	18m 57s
no-std (nightly-2023-08-05, macos-latest)	20m 47s
no-std (nightly-2023-08-05, windows-latest)	17m 21s
miri	57s
deny / deny	21s
docs / docs	21s
msrv / msrv	3m 11s
tidy / tidy	59s
	1h 21m 1s

Provide feedback