Move i18n for Comment Form component to Notes app I18n file

What does this MR do?

For #287686 (closed)

In #287686 (closed), we need to show a specific error message as it's returned from the API.

Since I'll be touching i18n strings and moving at least one to a setup like the recommended external file + $options setup, it makes sense to do due diligence and move everything at once.

MR	Notes
We're here 👉🏻	Since we're going to be touching strings and i18n values, this MR cleans up the existing i18n into a single central location for the Notes app
!55457 (merged)	New branched logic to show Flash messages specific to command-only errors

Screenshots (strongly suggested)

N/A, this is all backstage maintenance work.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team