fix: Enable MLKEM768X25519 by default #5486

Job	Run time
Ensure `Cargo.lock` contains all required dependencies	2s
toolchains	2s
check (ubuntu-latest, 1.76.0, debug)	2m 7s
check (ubuntu-latest, stable, debug)	1m 34s
check (ubuntu-latest, nightly, debug)	3m 4s
check (macos-latest, 1.76.0, debug)	1m 49s
check (macos-latest, stable, debug)	1m 45s
check (macos-latest, nightly, debug)	2m 35s
check (windows-latest, 1.76.0, debug)	4m 0s
check (windows-latest, stable, debug)	5m 7s
check (windows-latest, nightly, debug)	6m 26s
check (ubuntu-latest, stable, release)	1m 11s
bench	0s
	29m 42s

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