ci: Don't set `compiler-builtins-no-f16-f128` #2906

Job	Run time
build_system	31s
spell_check	7s
duplicates	3s
build (gcc-15.deb, --extended-rand-tests)	9m 37s
build (gcc-15.deb, --std-tests)	7m 9s
build (gcc-15.deb, --test-libcore)	17m 1s
build (gcc-15.deb, --extended-regex-tests)	12m 10s
build (gcc-15.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	11m 33s
build (gcc-15.deb, --extended-regex-example-tests)	7m 8s
build (gcc-15.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	11m 43s
build (gcc-15-without-int128.deb, --extended-regex-tests)	12m 32s
build (gcc-15-without-int128.deb, --extended-regex-example-tests)	7m 36s
build (gcc-15-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	12m 36s
build (gcc-15.deb, --projects)	10m 58s
build (gcc-15-without-int128.deb, --test-libcore)	16m 31s
build (gcc-15-without-int128.deb, --std-tests)	7m 3s
build (gcc-15-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	11m 23s
build (gcc-15-without-int128.deb, --projects)	12m 9s
build (gcc-15-without-int128.deb, --extended-rand-tests)	8m 34s
success	3s
	2h 56m 27s

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