Correct invalid class `gl-display-line` to `gl-display-inline`

What does this MR do and why?

Context

For #355771 (closed)

MR	Description
!82082 (closed)	Restructures (again) the restructured MR Widget for the Merged state. This MR uncovered the bug fixed in THIS MR.
We're here! 👉🏻	A bug identified in the Original Restructured MR Widget (which is still feature flagged), that uses a non-existent CSS class.

Changes

This MR updates the non-existent class gl-display-line to be gl-display-inline.

It also adds a · to the displayed output since they are now displayed inline, and need some separator.

Screenshots or screen recordings

Before (master)	After

How to set up and validate locally

1. Enable the restructured_mr_widget feature flag
2. Create an MR that has the text Closes [issue 1] and Related to [issue 2 in the description
   • [issue 1] and [issue 2] should be in the format #1 and #2 where 1 and 2 are actual issues in the project.
3. Make sure the MR is in a state that is ready to merge (no blocking threads, no merge conflicts, etc.)
4. Note the merge widget area

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.