stale: fix bug label name

Author: kashike

.github/stale.yml

@@ -9,7 +9,7 @@ exemptLabels:
   - 'status: accepted'
   - 'status: future'
   - 'status: wip'
-  - 'status: bug'
+  - 'type: bug'
 # Label to use when marking an issue as stale
 staleLabel: 'status: stale'
 # Comment to post when marking an issue as stale. Set to `false` to disable