fix: Enable MLKEM768X25519 by default #5544

Job	Run time
Ensure `Cargo.lock` contains all required dependencies	5s
toolchains	5s
check (ubuntu-latest, 1.76.0, debug)	47s
check (ubuntu-latest, stable, debug)	43s
check (ubuntu-latest, nightly, debug)	3m 3s
check (macos-latest, 1.76.0, debug)	1m 9s
check (macos-latest, stable, debug)	1m 22s
check (macos-latest, nightly, debug)	3m 0s
check (windows-latest, 1.76.0, debug)	2m 23s
check (windows-latest, stable, debug)	2m 38s
check (windows-latest, nightly, debug)	6m 21s
check (ubuntu-latest, stable, release)	1m 6s
bench	0s
	22m 42s

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