"taskName" changed to "label" as per version 2.0.0 (#2741)

https://code.visualstudio.com/docs/editor/tasks#_migrating-to-tasks-200

Author: anandlalvb

Code Samples/Fib/.vscode/tasks.json

@@ -4,7 +4,7 @@
     "version": "2.0.0",
     "tasks": [
         {
-            "taskName": "build",
+            "label": "build",
             "type": "shell",
             "group": {
                 "kind": "build",
@@ -47,4 +47,4 @@
             }
         }
     ]
-}
+}