Add clip to deploy.prototxt

samples/dnn/face_detector/deploy.prototxt

@@ -1784,6 +1784,7 @@ layer {
     }
     code_type: CENTER_SIZE
     keep_top_k: 200
-    confidence_threshold: 0.01
+    confidence_threshold: 0.2
+    clip: 1
   }
 }