Make scrollable tabs work with gl_tabs_nav helper
In !74007 (merged) there are scrollable tabs. In order to make them scrollable, we need to rely on non-Pajamas compliant classes.
An approach to fixing this was taken in !69298 (merged), but there are more tabs which are wider in !74007 (merged), and so the problem is more pronounced.
See also !70919 (merged), which extracted the gl_tabs_nav
helper out from !69298 (merged).
How this is implemented may depend on gitlab-ui#1940, since it'd be good to unify the code/approach used in both.
Edited by Mark Florian