Users: Hid lanuage preference for guest user

Hiding since it's not really used, and may mislead on how to set default
app language (which should be done via env options).
Updated test to cover.

For #5356

resources/views/users/edit.blade.php

@@ -34,7 +34,9 @@ class="setting-list-label">{{ trans('settings.users_avatar') }}</label>
                         </div>
                     </div>
 
-                    @include('users.parts.language-option-row', ['value' => old('language') ?? $user->getLocale()->appLocale()])
+                    @if(!$user->isGuest())
+                        @include('users.parts.language-option-row', ['value' => old('language') ?? $user->getLocale()->appLocale()])
+                    @endif
                 </div>
 
                 <div class="text-right">

tests/User/UserManagementTest.php

@@ -202,9 +202,13 @@ public function test_delete_removes_user_preferences()
     public function test_guest_profile_shows_limited_form()
     {
         $guest = $this->users->guest();
+
         $resp = $this->asAdmin()->get('/settings/users/' . $guest->id);
         $resp->assertSee('Guest');
-        $this->withHtml($resp)->assertElementNotExists('#password');
+        $html = $this->withHtml($resp);
+
+        $html->assertElementNotExists('#password');
+        $html->assertElementNotExists('[name="language"]');
     }
 
     public function test_guest_profile_cannot_be_deleted()