Resolve "Web IDE Status Bar is broken when System footer is present"

What does this MR do?

Adjusts the positioning of the Web IDE status bar if the System Footer message (EE only feature) is present.

Are there points in the code the reviewer needs to double check?

None that I can think of.

Why was this MR needed?

Broken, I believe, since 10.8.

Screenshots (if relevant)

Before
After

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
• EE specific content should be in the top level /ee folder
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them

What are the relevant issue numbers?

Closes #6305 (closed)