Code Quality: Remove mediaRecording feature flag code

[timarney]

Context

This feature has been enabled by default in v1.23.0.

Summary

Removes mediaRecording feature flag

Relevant Technical Choices

To-do

User-facing changes

Testing Instructions

• This is a non-user-facing change and requires no QA

This PR can be tested by following these steps:

1. Ensure Video Optimization via Settings is turned on
2. Create a story
3. Note the Record Video / Audio button is available by default
4. Record video + Insert video
5. Remove the video
6. With an empty canvas use the right click menu to select Record Video

Reviews

Does this PR have a security-related impact?

No

Does this PR change what data or activity we track or use?

No

Does this PR have a legal-related impact?

No

Checklist

• This PR addresses an existing issue and I have linked this PR to it in ZenHub
• I have tested this code to the best of my abilities
• I have verified accessibility to the best of my abilities (docs)
• I have verified i18n and l10n (translation, right-to-left layout) to the best of my abilities
• This code is covered by automated tests (unit, integration, and/or e2e) to verify it works as intended (docs)
• I have added documentation where necessary
• I have added a matching Type: XYZ label to the PR

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Fixes #11998

[googleforcreators-bot]

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