Update system-design.json fix typo (#4414)

src/data/roadmaps/system-design/system-design.json

@@ -3639,7 +3639,7 @@
                   "y": "9",
                   "properties": {
                     "size": "17",
-                    "text": "Layer 7 Load Blancing"
+                    "text": "Layer 7 Load Balancing"
                   }
                 }
               ]
@@ -10160,4 +10160,4 @@
   },
   "dependencies": [],
   "projectID": "file:///Users/kamrify/Desktop/New%20Roadmaps/New%20Project%201.bmpr"
-}
+}