Fix fluid width invite members banner
What does this MR do and why?
Fix fluid width invite members banner
- incorrect as it didn't comply to the page and line up in margins before.
- incorrectly under broadcast-wrapper
- see https://design.gitlab.com/components/banner#placement for guide on alignment
Changelog: fixed
Screenshots or screen recordings
| type | Before | After |
|---|---|---|
| fluid width |  |
 |
| fixed |  |
no change |
How to set up and validate locally
- Create a new group.
- change your user preferences between fixed and fluid to see.
MR acceptance checklist
Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.
Related to #530958