[CI] Address hax-action issues

[jschneider-bensch]

• Very long runtimes: This is long enough to make GH treat the job as non-responsive, and it will therefor be kicked from the merge queue
  • 1h 18min on SHA-3
  • 1h 11min on ML-KEM
• Flakehub registration error: Are we using this correctly?

[FlakeHub registration required.](https://github.com/cryspen/libcrux/actions/runs/20924686792/job/60119284366#step:3:291)
Unable to authenticate to FlakeHub. Individuals must register at FlakeHub.com; Organizations must create an organization at FlakeHub.com.

• Unexpected input warning: I don't know if this is significant

[extract](https://github.com/cryspen/libcrux/actions/runs/20924686792/job/60119284366#step:3:9)
Unexpected input(s) 'determinate', valid inputs are ['backtrace', 'extra-args', 'extra-conf', 'github-token', 'init', 'local-root', 'log-directives', 'logger', 'ssl-cert-file', 'pproxy', 'mac-case-sensitive', 'mac-encrypt', 'mac-root-disk', 'mac-volume-label', 'modify-profile', 'nix-build-group-id', 'nix-build-group-name', 'nix-build-user-base', 'nix-build-user-count', 'nix-build-user-prefix', 'nix-installer-branch', 'nix-installer-pr', 'nix-installer-revision', 'nix-installer-tag', 'nix-installer-url', 'nix-package-url', 'planner', 'reinstall', 'start-daemon', 'diagnostic-endpoint', 'trust-runner-user']

[jschneider-bensch]

The lower two are addressed by hacspec/hax-actions#11.

We identified the issue behind long runtimes and track it in hacspec/hax-actions#12.

[jschneider-bensch]

hacspec/hax-actions#12 is solved now, closing this as well.