Remove stale and obsolete from PR's on update (#3431)

Bug example: #1782

Shouldn't have closed, but instead was. I assume because it was still
labeled as "obsolete", and it had been 30 days - but only the stale
label had been removed.

I added `labels-to-remove-when-unstale` to all the operations, since I'm
not sure which operation does the work (and figured it couldn't hurt).

.github/workflows/close.yaml

@@ -43,3 +43,4 @@ jobs:
           close-issue-reason: not_planned
           stale-issue-label: wontfix
           enable-statistics: true
+          labels-to-remove-when-unstale: stale,obsolete

.github/workflows/obsolete.yaml

@@ -39,6 +39,7 @@ jobs:
             'awaiting-maintainer' label. Thank you for your contributions
           stale-issue-label: obsolete
           only-labels: stale
+          labels-to-remove-when-unstale: stale,obsolete
           exempt-issue-labels: awaiting-maintainer
           remove-stale-when-updated: true
           ascending: true

.github/workflows/stale.yaml

@@ -42,3 +42,4 @@ jobs:
           exempt-issue-labels: awaiting-maintainer, obsolete
           ascending: true
           enable-statistics: true
+          labels-to-remove-when-unstale: stale,obsolete