keycloak: unbreak arch theme with keycloak 17.0.0

commit 100dbb8781d780d35ad0569222bcda3ef85bbe0a upstream.

roles/keycloak/files/theme/archlinux/account/index.ftl

@@ -62,7 +62,9 @@
 
             <#if msg??>
                 var locale = '${locale}';
-                var l18nMsg = JSON.parse('${msgJSON?no_esc}');
+                <#outputformat "JavaScript">
+                var l18nMsg = JSON.parse('${msgJSON?js_string}');
+                </#outputformat>
             <#else>
                 var locale = 'en';
                 var l18Msg = {};