Update json_helper.py

One of the default parameters contains a potential spelling mistake which might confuse users. I've just downloaded this repo locally and am looking forward to trying it out. Thanks for sharing!

json_helper.py

@@ -17,7 +17,7 @@ json_content = """{{
     "education": [
         {{
             "institute_name": "",
-            "year_of_passsing": "",
+            "year_of_passing": "",
             "score": ""
         }},
         {{