Add localization string for policy-managed setting message

Co-authored-by: BornToBeRoot <16019165+BornToBeRoot@users.noreply.github.com>

Author: Copilot

Source/NETworkManager.Localization/Resources/Strings.Designer.cs

@@ -3960,4 +3960,7 @@ If you click Cancel, the profile file will remain unencrypted.</value>
   <data name="HelpMessage_MaximumNumberOfBackups" xml:space="preserve">
     <value>Number of backups that are retained before the oldest one is deleted.</value>
   </data>
+  <data name="SettingManagedByAdministrator" xml:space="preserve">
+    <value>This setting is managed by your administrator.</value>
+  </data>
 </root>

Source/NETworkManager.Localization/Resources/Strings.resx

@@ -30,7 +30,7 @@
                 </Rectangle.Resources>
             </Rectangle>
         </StackPanel>
-        <TextBlock Text="This setting is managed by your administrator."
+        <TextBlock Text="{x:Static localization:Strings.SettingManagedByAdministrator}"
                    Foreground="Orange"
                    Margin="0,0,0,10"
                    Visibility="{Binding IsUpdateCheckManagedByPolicy, Converter={StaticResource BooleanToVisibilityCollapsedConverter}}" />