Add missing IndexShard#readAllowed()

This was lost in #33835

Author: s1monw

server/src/main/java/org/elasticsearch/index/shard/IndexShard.java

@@ -914,6 +914,7 @@ public FlushStats flushStats() {
     }
 
     public DocsStats docStats() {
+        readAllowed();
         return getEngine().docStats();
     }