Update rust toolchain to 2024-02-20 #316

Job	Run time
build (gcc-13.deb, --mini-tests)	54s
build (gcc-13.deb, --std-tests)	49s
build (gcc-13.deb, --test-libcore)	49s
build_system	24s
build (gcc-13.deb, --extended-rand-tests)	47s
duplicates	3s
build (gcc-13.deb, --extended-regex-tests)	1m 7s
build (gcc-13.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	48s
build (gcc-13.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	45s
build (gcc-13.deb, --projects)	1m 1s
build (gcc-13-without-int128.deb, --mini-tests)	47s
build (gcc-13-without-int128.deb, --std-tests)	45s
build (gcc-13-without-int128.deb, --test-libcore)	59s
build (gcc-13-without-int128.deb, --extended-rand-tests)	1m 14s
build (gcc-13-without-int128.deb, --extended-regex-tests)	1m 8s
build (gcc-13-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	1m 0s
build (gcc-13-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	1m 11s
build (gcc-13-without-int128.deb, --projects)	1m 0s
	15m 31s

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