Center the header logo

Originally opened at !6507 (closed) by @AshleyDumaine.

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What does this MR do?

• Centers the header logo using relative positioning on the svg or img in the header-logo

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

Why was this MR needed?

The custom wide header logos aren't centered after logging in as seen in #22494 (closed)

Screenshots (if relevant)

Before	After

Signout (for centering comparison):

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Tests
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #22494 (closed)