fix: show re-enable 2FA button when is2faenabled is null/undefined

After disabling 2FA via setupUserTwoFactorAuthentication, the API may
return is2faenabled as null or undefined rather than boolean false.
The strict equality check (=== false) prevented the "Setup 2FA" button
from appearing in those cases, making it impossible to re-enable 2FA.

Change the check to a falsy check (!record.is2faenabled) so the button
is shown whenever 2FA is not enabled, regardless of whether the value
is false, null, or undefined.

Fixes: #13233

Author: DaanHoogland

ui/src/config/section/user.js

@@ -179,7 +179,7 @@ export default {
       dataView: true,
       popup: true,
       show: (record, store) => {
-        return (record.is2faenabled === false && record.id === store.userInfo.id)
+        return (!record.is2faenabled && record.id === store.userInfo.id)
       },
       component: shallowRef(defineAsyncComponent(() => import('@/views/iam/SetupTwoFaAtUserProfile.vue')))
     },