[JS] the replace statement in parseDate is too greedy (#8632) (#8633)

* updated the regex used in the String.replace for parseDate() to more precisely target ISO-8601
* added the replace function call to the ES6 mustache file

samples/client/petstore/javascript-es6/src/ApiClient.js

@@ -512,7 +512,7 @@ class ApiClient {
     */
     static parseDate(str) {
         if (isNaN(str)) {
-            return new Date(str);
+            return new Date(str.replace(/(\d)(T)(\d)/i, '$1 $3'));
         }
         return new Date(+str);
     }