Fix CSS grid on a new Project/Group Milestone

What does this MR do?

Fixes CSS grid on a new Project/Group Milestone Web page.

What are the relevant issue numbers?

Closes #56764 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [n/a] Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• [n/a] Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• [n/a] Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• [n/a] Security reports checked/validated by reviewer

Screenshots

after the MR

project	group