fix: incorrect csv import example on frontend

Example given for CSV import on Import.vue is incorrect since
field `attributes` value is not a valid JSON. Previous example
copy pasted was throwing CSV parse error.

frontend/src/views/Import.vue

@@ -99,14 +99,12 @@
           <code className="csv-row">
             <span>user1@mail.com,</span>
             <span>"User One",</span>
-            <span>{'"{""age"": 42, ""planet"": ""Mars""}"'}</span>
+            <span>"{""age"": 42, ""planet"": ""Mars""}"</span>
           </code><br />
           <code className="csv-row">
             <span>user2@mail.com,</span>
             <span>"User Two",</span>
-            <span>
-              {'"{""age"": 24, ""job"": ""Time Traveller""}"'}
-            </span>
+            <span>"{""age"": 24, ""job"": ""Time Traveller""}"</span>
           </code>
         </blockquote>
       </div>