remove stale bot in favor of mattermod (#10428)

.github/stale.yml

@@ -1,37 +0,0 @@
-# Configuration for probot-stale - https://github.com/probot/stale
-
-# Number of days of inactivity before an Issue or Pull Request becomes stale
-daysUntilStale: 14
-
-# Number of days of inactivity before an Issue or Pull Request with the stale label is closed.
-# Set to false to disable. If disabled, issues still need to be closed manually, but will remain marked as stale.
-daysUntilClose: false
-
-# Issues or Pull Requests with these labels will be ignored by the stale bot. Set to `[]` to disable.
-exemptLabels:
-  - Lifecycle/2:inactive
-  - Lifecycle/3:orphaned
-  - Lifecycle/frozen
-
-# Set to true to ignore issues in a project (defaults to false)
-exemptProjects: true
-
-# Set to true to ignore issues in a milestone (defaults to false)
-exemptMilestones: false
-
-# Set to true to ignore issues with an assignee (defaults to false)
-exemptAssignees: false
-
-# Label to use when marking as stale
-staleLabel: Lifecycle/1:stale
-
-# Comment to post when marking as stale. Set to `false` to disable
-markComment: >
-  This issue has been automatically labelled "stale" because it hasn't had recent activity.
-  A core team member will check in on the status of the PR to help with questions.
-  Thank you for your contribution!
-  /cc @hanzei @jasonblais
-
-# Limit to only `issues` or `pulls`
-only: pulls
-