fixed missing bracket

frontend/app/data/en.json

@@ -50,7 +50,8 @@
   "warnings": {
     "CHECK_QUESTION_NAME": "Couldn't find the end of the name. Name should be followed by hypen (-).",
     "UNKNOWN_PARAGRAPH_TYPE": "Unknown paragraph type",
-    "REGEX_RESTRICTION": "Moodle has some restrictions for regex. There is a list of meta characters which you cannot youse: . ^ $ * + { } \\ / . Read more about regex in Moodle: https://docs.moodle.org/404/en/Regular_Expression_Short-Answer_question_type. Coursera supports the Java regular expression format. Use a regular expression tester, like RegexPlanet, to check syntax: http://www.regexplanet.com/advanced/java/index.html",
+    "REGEX_RESTRICTION": "Moodle has some restrictions for regex. There is a list of meta characters which you cannot youse: . ^ $ * + { } \\ / . Read more about regex in Moodle: https://docs.moodle.org/404/en/Regular_Expression_Short-Answer_question_type. Coursera supports the Java regular expression format. Use a regular expression tester, like RegexPlanet, to check syntax: http://www.regexplanet.com/advanced/java/index.html"
+  },
   "question_types": {
     "SINGLE_CHOICE": "Single Choice",
     "MULTIPLE_CHOICE": "Multiple Choice",