don't mark blocked issues as stale

[ci skip]

.github/stale.yml

@@ -6,6 +6,7 @@ daysUntilClose: 30
 exemptLabels:
   - type:security-issue # never close automatically
   - state:awaiting-response # handled by different bot
+  - state:blocked
 # Set to true to ignore issues in a milestone (defaults to false)
 exemptMilestones: true
 # Label to use when marking an issue as stale