Widen issuable list only on mobile to be mobile-friendly

What does this MR do?

Widen issuable list (Issue list, MR list and Epics list) only on mobile to be mobile-friendly.

cf. !41244 (merged) for TODO list-specific

Screenshots

issuable	before	after
Issues
Epics

cf. after v1 screenshot for issues

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [n/a] Documentation (if required)
• Code review guidelines
• [n/a] Merge request performance guidelines
• Style guides
• [n/a] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done