fixed typo (#982)

Author: mohammed-ali-1

README.md

@@ -52,7 +52,7 @@ parse-dashboard --dev --appId yourAppId --masterKey yourMasterKey --serverURL "h
 
 You may set the host, port and mount path by supplying the `--host`, `--port` and `--mountPath` options to parse-dashboard. You can use anything you want as the app name, or leave it out in which case the app ID will be used.
 
-NB: the `--dev` parameter is disabling production-ready security features, do not use this parameter when starting the dashboard in production. This parameter is useful is you are running on docker. 
+NB: the `--dev` parameter is disabling production-ready security features, do not use this parameter when starting the dashboard in production. This parameter is useful if you are running on docker. 
 
 After starting the dashboard, you can visit http://localhost:4040 in your browser: