webhooks/teamcity: Change teamcity build triggering user to iago.

To be able to get a screenshot of the personal message using the
`generate-integration-docs-screenshot` tool, this commit changes the
personal build to be triggered by iago, instead of cordelia.

zerver/webhooks/teamcity/fixtures/personal.json

@@ -52,9 +52,9 @@
         "name": "env.BUILD_IS_PERSONAL",
         "value": "true"
       },
-	  {
+      {
       "name": "teamcity.build.triggeredBy.username",
-      "value": "cordelia"
+      "value": "iago"
       }
     ]
   }