Change "Nothing to merge" widget

What does this MR do and why?

• Change the "Nothing to merge" widget appearance like other widgets.
• Fix "Ready to merge" widget title align.

Example of all the widgets

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.

1. Go to any issue
2. Click [Create MR]
3. See new MR with "Nothing to merge" widget
4. Commit changes
5. Wait for the pipeline to become green
6. See "Ready to merge" widget

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.

#425468 (closed)