Updating Site URL help text in System Console (#6582)

* Updating Site URL help text in System Console

* Replacing single quotes with double quotes

* Corrected statement about non-standard ports

* Converted double quotes to single quotes

webapp/components/admin_console/configuration_settings.jsx

@@ -105,7 +105,7 @@ export default class ConfigurationSettings extends AdminSettings {
                     helpText={
                         <FormattedMessage
                             id='admin.service.siteURLDescription'
-                            defaultMessage='The URL, including port number and protocol, that users will use to access Mattermost. This setting is required.'
+                            defaultMessage='The URL that users will use to access Mattermost. Standard ports, such as 80 and 443, can be omitted, but non-standard ports are required. For example: http://mattermost.example.com:8065. This setting is required.'
                         />
                     }
                     value={this.state.siteURL}