Fix alignment of issuable sidebar header
What does this MR do and why?
- Fixes alignment of collapse icon in issuable sidebar behind feature flag
:notifications_todos_buttons - Fix vertical alignment of epic sidebar header
Screenshots or screen recordings
| Before | After | |
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| Issue |  |
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| Epic |  |
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| Epic (collapsed) |  |
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How to set up and validate locally
- Enable
:notifications_todos_buttons - Check issue and epic