Breaks GitHub's new Custom Notifications UI #3745

<img align=right src=https://user-images.githubusercontent.com/886627/99826391-23324b80-2b0d-11eb-9ce9-8b77bc3f918d.png>

I've tested this with the extension both on and off, and it definitely seems to be due to Refined GitHub! To replicate, try clicking the new Custom option from any repo's Watch dropdown.

• Current Behavior: With the extension on, the customization panel does open very briefly, but then the Watch dropdown automatically closes itself...
• Expected Behavior: A secondary customization panel (pictured) should slide, and stay, open!

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