Chore: Remove unused setPanelSubtitle from code

Lindsey Sheltonrequested to merge
619527-remove-setPanelSubtitle-from-codebase into master

What does this MR do and why?

This MR is a cleanup maintenance MR. We are removing the references to unused functionality for setPanelSubtitle.

References

Screenshots or screen recordings

N/A. This is removing unused code.

How to set up and validate locally

N/A. This is removing unused code.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #619527 (closed)

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