Fixed extra margin when the merge request tabs are affixed
This was caused by some weird padding that was on the container & then
not correctly removed.
The fix involved removing the container from inside the tabs holder div
& then adding the widths through CSS depending on if fixed & whether the
parent is limited width or not.
In reality out container classes need to be fixed as it is getting pretty un-managable at the moment this should of been an easy fix, but in reality turned into something much harder.
Closes#26853
