Hide code quality annotation space when feature flag is disabled

What does this MR do?

In !57926 (merged) we introduced inline code quality annotations behind the feature flag :codquality_mr_diff_annotations, but did not check for the feature flag before adding the space that the icons will appear in 😅 so files with new code quality degradations are inexplicably indented 20px more than files without them:

from a thread in #is-this-known (internal link)

This MR checks for the feature flag :codquality_mr_diff_annotations before we add the with-codequality class to the diff grid, so that the column for the code quality annotations is only expanded from 0 to 20px when the feature flag is enabled.

Screenshots (strongly suggested)

what happens now	what should happen with this MR
the second file is indented more for no reason	indentation is the same across all files

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Related to #2526 (closed)