Code Quality: Rename 'default' to 'Use system setting'

Author: yaira2

src/Files.App/Data/Items/AppLanguageItem.cs

@@ -30,7 +30,7 @@ public AppLanguageItem(string code, bool systemDefault = false)
 			if (systemDefault || string.IsNullOrEmpty(code))
 			{
 				Code = new CultureInfo(code).Name;
-				Name = Strings.SettingsPreferencesSystemDefaultLanguageOption.GetLocalizedResource();
+				Name = Strings.UseSystemSetting.GetLocalizedResource();
 			}
 			else
 			{

src/Files.App/Strings/en-US/Resources.resw

@@ -309,6 +309,9 @@
   <data name="DarkTheme" xml:space="preserve">
     <value>Dark</value>
   </data>
+  <data name="UseSystemSetting" xml:space="preserve">
+    <value>Use system setting</value>
+  </data>
   <data name="Application" xml:space="preserve">
     <value>Application</value>
   </data>
@@ -524,9 +527,6 @@
   <data name="Status" xml:space="preserve">
     <value>Status</value>
   </data>
-  <data name="SettingsPreferencesSystemDefaultLanguageOption" xml:space="preserve">
-    <value>Windows default</value>
-  </data>
   <data name="NavigationToolbarVisiblePathNoResults" xml:space="preserve">
     <value>No results</value>
   </data>

src/Files.App/ViewModels/Settings/AppearanceViewModel.cs

@@ -39,7 +39,7 @@ public AppearanceViewModel(IUserSettingsService userSettingsService, IResourcesS
 
 			Themes =
 			[
-				Strings.Default.GetLocalizedResource(),
+				Strings.UseSystemSetting.GetLocalizedResource(),
 				Strings.LightTheme.GetLocalizedResource(),
 				Strings.DarkTheme.GetLocalizedResource()
 			];