ci: remove stale bot

.github/stale.yml

-# Number of days of inactivity before an issue becomes stale
-daysUntilStale: 30
-# Number of days of inactivity before a stale issue is closed
-daysUntilClose: 30
-# Only issues or pull requests with all of these labels are check if stale. Defaults to `[]` (disabled)
-onlyLabels:
-  - ":rocket: feature"
-  - ":dna: enhancement"
-# Label to use when marking an issue as stale
-staleLabel: up-for-grabs
-# Limit to only `issues` not `pulls`
-only: issues
-# Comment to post when marking an issue as stale. Set to `false` to disable
-markComment: >
-  This issue has been automatically marked as up-for-grabs because it has not had
-  recent activity. It will be closed if no further activity occurs. Thank you
-  for your contributions.
-# Comment to post when closing a stale issue. Set to `false` to disable
-closeComment: false
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