VS: Remove empty ExternalWarningLevel entry from flag table for v143

Templates/MSBuild/FlagTables/v143_CL.json

@@ -609,13 +609,6 @@
     "value": "Level4",
     "flags": []
   },
-  {
-    "name": "ExternalWarningLevel",
-    "switch": "",
-    "comment": "Inherit Project Warning Level",
-    "value": "InheritWarningLevel",
-    "flags": []
-  },
   {
     "name": "CallingConvention",
     "switch": "Gd",