Fix bleeding of page size selector in vulnerability report grouping

What does this MR do and why?

When there is only 1 page of results and the vulnerability report is grouped by status or severity, the page size selector dropdown bleeds into the next group.

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

1. Go to security-reports vulnerability report
2. Group by "Severity"
3. Open severity "Unknown" or other with less than 20 results
4. Validate it does not bleed in next row and page size selector is right-aligned
5. Make browser narrow to mobile screen size and validate it stays on the right
6. Open severity "High" or other with more than 20 results
7. Validate that prev/next cursor buttons are center aligned and page size selector is still right aligned

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 #428427 (closed)