Update ldap_settings.jsx (#3508)

* Update ldap_settings.jsx

Changed help text for consistency

* Update en.json

webapp/components/admin_console/ldap_settings.jsx

@@ -213,7 +213,7 @@ export default class LdapSettings extends AdminSettings {
                     helpText={
                         <FormattedMessage
                             id='admin.ldap.userFilterDisc'
-                            defaultMessage='Optionally enter an LDAP Filter to use when searching for user objects. Only the users selected by the query will be able to access Mattermost. For Active Directory, the query to filter out disabled users is (&(objectCategory=Person)(!(UserAccountControl:1.2.840.113556.1.4.803:=2))).'
+                            defaultMessage='(Optional) Enter an LDAP Filter to use when searching for user objects. Only the users selected by the query will be able to access Mattermost. For Active Directory, the query to filter out disabled users is (&(objectCategory=Person)(!(UserAccountControl:1.2.840.113556.1.4.803:=2))).'
                         />
                     }
                     value={this.state.userFilter}