PLT-3766 Change LDAP references to AD/LDAP in the UI (#3925)

webapp/components/admin_console/email_authentication_settings.jsx

@@ -58,7 +58,7 @@ export default class EmailAuthenticationSettings extends AdminSettings {
                     helpText={
                         <FormattedMessage
                             id='admin.email.allowSignupDescription'
-                            defaultMessage='When true, Mattermost allows team creation and account signup using email and password.  This value should be false only when you want to limit signup to a single-sign-on service like OAuth or LDAP.'
+                            defaultMessage='When true, Mattermost allows team creation and account signup using email and password.  This value should be false only when you want to limit signup to a single-sign-on service like OAuth or AD/LDAP.'
                         />
                     }
                     value={this.state.enableSignUpWithEmail}