Don't add text to markdown buttons

What does this MR do and why?

!98868 (merged) introduced a regression to the markdown buttons. This removes the text that was added to the buttons.

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Test creating a new MR
• Verify that the attach and expand buttons don't have text next to the icons

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #363904 (closed)