Update icon on the file-tree in changes tab for MR page

What does this MR do and why?

Update the icon on the file-tree : #443614 (closed)

Discussion about the icon can be found here: #443614[MR_Changes_Tab.png] (comment 1829339160)

MR acceptance checklist

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

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.