Fixed level 6 missing

screens/Tetris/GameLogic.js

@@ -23,11 +23,11 @@ export default class GameLogic {
         '3': 500,
         '4': 700,
         '5': 1000,
-        '7': 1500,
-        '8': 2000,
-        '9': 3000,
-        '10': 4000,
-        '11': 5000,
+        '6': 1500,
+        '7': 2000,
+        '8': 3000,
+        '9': 4000,
+        '10': 5000,
     };
 
     currentGrid: Array<Array<Object>>;