Drop duplicate "updated xx hours ago" text in PR lists sorted by last update #3948

On PR lists sorted by "last update", GitHub automatically shows when it was updated. This date often matches the closed/merged date, so it's redundant:

<img width="517" alt="Screen Shot 2" src="https://user-images.githubusercontent.com/1402241/107077327-4a1a2880-67b2-11eb-8ad4-172f77c1158e.png">

We could hide the "updated 19 hours ago" if the datetime matches exactly. This is also helpful to spot any issues and PRs that received comments after the closure since they'll be the only ones with the "updated XXX" label