clean up gibot configuration (#6686)

It is no longer used since we enabled stale bot.

.gibot.yml

@@ -1,56 +0,0 @@
-stages:
-  mark_for_closing:
-     days: 30
-     labels:
-       - status/need more info
-       - status/invalid
-       - status/can't reproduce
-       - status/wontfix
-     exclude:
-       - status/marked for cleanup
-       - status/accepting-pr
-     comment:
-       - 'Hello @{author}! There has been no activity on this ticket for over a period of {days} days. I am automatically replying to let you know we will close this ticket within 1 week due to inactivity and consider this resolved.'
-       - 'If you believe this is in error, please reply with the requested information.'
-       - 'Thank you. :robot:'
-     action:
-       close: false
-       comment: true
-       assign_label:
-         - status/marked for cleanup
-  clean_up:
-     days: 7
-     labels:
-       - status/marked for cleanup
-     comment:
-       - 'Hello @{author}! We have detected no activity for {days} days on this ticket. We therefore assume that the original reporter has lost interest or the issue has been resolved.'
-       - 'Since we have marked this ticket for deletion, we will be closing it.'
-       - 'If this has been closed in error, please create a comment below and we can reopen this issue. Note that you may need to provide additional information that was requested.'
-       - 'Thank you. :robot:'
-     action:
-       close: true
-       comment: true
-       assign_label:
-         - status/closed by bot
-       remove_label:
-         - status/marked for cleanup
-  remind_about_old_ticket:
-    days: 365
-    labels:
-      - kind/bug
-      - kind/critical bug
-    exclude:
-      - status/need more info
-      - status/invalid
-      - status/can't reproduce
-      - status/wontfix
-      - status/marked for cleanup
-      - status/inactive
-      - status/stale
-      - status/accepting-pr
-    comment:
-      - 'Hello @acemod/maintainers. This ticket has been open for over {days} days without any activity.'
-    action:
-      comment: true
-      assign_label:
-       - status/inactive