Allow the Lock bot to lock existing closed issues

.github/lock.yml

@@ -5,7 +5,7 @@ daysUntilLock: 90
 
 # Skip issues and pull requests created before a given timestamp. Timestamp must
 # follow ISO 8601 (`YYYY-MM-DD`). Set to `false` to disable
-skipCreatedBefore: 2020-01-01
+skipCreatedBefore: false
 
 # Issues and pull requests with these labels will be ignored. Set to `[]` to disable
 exemptLabels: []