remove unused error message 2568

Author: a-tarasyuk

src/compiler/diagnosticMessages.json

@@ -2056,10 +2056,6 @@
         "category": "Error",
         "code": 2567
     },
-    "Type '{0}' is not an array type. Use compiler option '--downlevelIteration' to allow iterating of iterators.": {
-        "category": "Error",
-        "code": 2568
-    },
     "Type '{0}' is not an array type or a string type. Use compiler option '--downlevelIteration' to allow iterating of iterators.": {
         "category": "Error",
         "code": 2569