[chore] delete stale bot yaml config

The stale bot was removed so there's no use for having the config anymore

.github/stale.yml

@@ -1,52 +0,0 @@
-# Configuration for probot-stale - https://github.com/probot/stale
-
-# Only issues or pull requests with all of these labels are check if stale. Defaults to `[]` (disabled)
-onlyLabels: []
-
-# Issues or Pull Requests with these labels will never be considered stale. Set to `[]` to disable
-exemptLabels:
-  - popular
-  - pinned
-  - security
-  - bug
-  - "[Status] Maybe Later"
-
-# Set to true to ignore issues in a project (defaults to false)
-exemptProjects: false
-
-# 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: stale-bot
-
-# Comment to post when removing the stale label.
-# unmarkComment: >
-#   Your comment here.
-
-# Limit the number of actions per hour, from 1-30. Default is 30
-limitPerRun: 1
-
-# Optionally, specify configuration settings that are specific to just 'issues' or 'pulls':
-pulls:
-  daysUntilStale: 210
-  daysUntilClose: 25
-  markComment: >
-    This pull request has been automatically marked as stale because it has not had
-    recent activity. It will be closed if no further activity occurs. Thank you
-    for your contributions.
-  closeComment: >
-    This pull request has been closed as it was previously marked as stale and saw no subsequent activity.
-
-issues:
-  daysUntilStale: 180
-  daysUntilClose: 14
-  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. Thank you
-    for your contributions.
-  closeComment: >
-    This issue has been closed as it was previously marked as stale and saw no subsequent activity.