chore: remove stale bot for central repo (#564)

.github/stale.yml

-# Number of days of inactivity before an issue becomes stale
-daysUntilStale: 14
-# Number of days of inactivity before a stale issue is closed
-daysUntilClose: 21
-# Issues with these labels will never be considered stale
-exemptLabels:
-  - keep fresh
-# Label to use when marking an issue as stale
-staleLabel: stale
-# Comment to post when marking an issue as stale. Set to `false` to disable
-markComment: >
-  This issue has been automatically marked as stale because it has not had
-  recent activity. It will be closed if no further activity occurs.
-# Comment to post when closing a stale issue. Set to `false` to disable
-closeComment: >
-  This issue has been automatically closed for inactivity. If you still wish to
-  make these changes, please open a new pull request or reopen this one.