added checked to admin only

because it is confusing if you go straight to `Manually set the username and password.` and you can't go next since nothing is checked above but it becomes hidden

html/setup.html

@@ -137,7 +137,7 @@
                         <input type="radio" class="mr-2" name="ui-jellyfin_login" value="true" checked><span>{{ .lang.Login.authorizeWithJellyfin }}</span>
                     </label>
                     <label class="row switch pl-4 pb-4">
-                        <input type="checkbox" class="mr-2" id="ui-admin_only"><span>{{ .lang.Login.adminOnly }}</span>
+                        <input type="checkbox" class="mr-2" id="ui-admin_only" checked><span>{{ .lang.Login.adminOnly }}</span>
                     </label>
                     <label class="row switch pl-4 pb-2">
                         <input type="checkbox" class="mr-2" id="ui-allow_all"><span>{{ .lang.Login.allowAll }}</span>