Work item page right side is clipped on mobile with wide or unwrappable content
### Summary
On mobile viewports, the Work item page uniformly clips the right side of the entire page
when it includes wide or unwrappable content, including the Development widget for linked MR.
MR pages are unaffected.
### Steps to reproduce
1. Create a Work item.
1. Link the Work item to a MR so that the Development widget appears.
1. Open the Work item on a mobile device or in Chrome DevTools mobile emulation.
### Example
#600461
### What is the current *bug* behavior?
Content on the right side is clipped and unreadable,
with no horizontal scroll available:
{width=278 height=600}
### What is the expected *correct* behavior?
Content should fit within the viewport without clipping,
as the MR page already does.
### Output of checks
This bug happens on GitLab.com
issue