chore: remove ffmpeg dependency from firefox nativeDeps in Ubuntu 22.04

[mxschmitt]

• As of today we don't have ffmpeg included in our 24.04 builds
• As of today the tests seem to be passing in 24.04
• 22.04 tests are also passing without ffmpeg
• Since 24.04 already lives without it, I think we don't need any docker.md adjustments to optionally include it

[github-actions]

Test results for "tests 1"

1 failed
❌ [firefox-library] › tests/library/capabilities.spec.ts:67:3 › should play video @smoke @firefox-ubuntu-22.04-node18

2 flaky

⚠️ [firefox-page] › tests/page/page-evaluate.spec.ts:403:3 › should throw for too deep reference chain @firefox-ubuntu-22.04-node18
⚠️ [playwright-test] › tests/ui-mode-test-watch.spec.ts:145:5 › should watch all @windows-latest-node18-1

38657 passed, 792 skipped
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Merge workflow run.