Resolve "Breadcrumb hidden by system message"

What does this MR do?

Adjusts the spacing left at the top of the page for the scenario:

• System Header message is present
• performance bar is not present

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

There is another open MR affecting vertical positioning of elements on the Web IDE page that solve the IDE status bar being covered by the system footer. Mentioning, as you might see this issue but it's unrelated to this MR.

Why was this MR needed?

Regression.

Screenshots (if relevant)

(Before fix)

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 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 #6313 (closed)