Use `folder-open` from sprite icons for Browse Files button in Tag page

What does this MR do?

Updates Browse Files button icon in Tag page to match with that of Commit page.

Screenshots

Before	After

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides

Closes #58274 (closed)