firefox: update expected container settings

[brckd]

Description

Fixes the outdated test result from #4851 (comment).

Checklist

• Change is backwards compatible.

• Code formatted with ./format.
  Nothing to format.

• Code tested through nix-shell --pure tests -A run.all or nix develop --ignore-environment .#all using Flakes.
  Only tested the updated test.

• Test cases updated/added. See example.
  Updated firefox-profile-settings.

• Commit messages are formatted like

  {component}: {description}
  
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• If this PR adds a new module

  • Added myself as module maintainer. See example.

Maintainer CC

@rycee @kira-bruneau

[DamienCassou]

Thank you, good job.