Fix typo

Author: ahejlsberg

src/compiler/checker.ts

@@ -30524,7 +30524,7 @@ namespace ts {
             }
             else if (node.operator === SyntaxKind.ReadonlyKeyword) {
                 if (node.type.kind !== SyntaxKind.ArrayType && node.type.kind !== SyntaxKind.TupleType) {
-                    return grammarErrorOnFirstToken(node, Diagnostics.readonly_type_modifier_is_only_permitted_on_array_and_typle_types, tokenToString(SyntaxKind.SymbolKeyword));
+                    return grammarErrorOnFirstToken(node, Diagnostics.readonly_type_modifier_is_only_permitted_on_array_and_tuple_types, tokenToString(SyntaxKind.SymbolKeyword));
                 }
             }
         }

src/compiler/diagnosticMessages.json

@@ -1023,7 +1023,7 @@
         "category": "Error",
         "code": 1353
     },
-    "'readonly' type modifier is only permitted on array and typle types.": {
+    "'readonly' type modifier is only permitted on array and tuple types.": {
         "category": "Error",
         "code": 1354
     },