chore: document deprecated systemPreferences APIs (#39343)

* chore: document deprecated systemPreferences APIs

* chore: forgot systemPreferences.appLevelAppearance

* test: expect deprecation messages

docs/api/system-preferences.md

@@ -417,7 +417,7 @@ Returns an object with system animation settings.
 
 ## Properties
 
-### `systemPreferences.appLevelAppearance` _macOS_
+### `systemPreferences.appLevelAppearance` _macOS_ _Deprecated_
 
 A `string` property that can be `dark`, `light` or `unknown`. It determines the macOS appearance setting for
 your application. This maps to values in: [NSApplication.appearance](https://developer.apple.com/documentation/appkit/nsapplication/2967170-appearance?language=objc). Setting this will override the

docs/breaking-changes.md

@@ -63,6 +63,41 @@ w.webContents.getPrintersAsync().then((printers) => {
 })
 ```
 
+### Deprecated: `systemPreferences.{get,set}AppLevelAppearance` and `systemPreferences.appLevelAppearance`
+
+The `systemPreferences.getAppLevelAppearance` and `systemPreferences.setAppLevelAppearance`
+methods have been deprecated, as well as the `systemPreferences.appLevelAppearance` property.
+Use the `nativeTheme` module instead.
+
+```js
+// Deprecated
+systemPreferences.getAppLevelAppearance()
+// Replace with
+nativeTheme.shouldUseDarkColors
+
+// Deprecated
+systemPreferences.appLevelAppearance
+// Replace with
+nativeTheme.shouldUseDarkColors
+
+// Deprecated
+systemPreferences.setAppLevelAppearance('dark')
+// Replace with
+nativeTheme.themeSource = 'dark'
+```
+
+### Deprecated: `alternate-selected-control-text` value for `systemPreferences.getColor`
+
+The `alternate-selected-control-text` value for `systemPreferences.getColor`
+has been deprecated. Use `selected-content-background` instead.
+
+```js
+// Deprecated
+systemPreferences.getColor('alternate-selected-control-text')
+// Replace with
+systemPreferences.getColor('selected-content-background')
+```
+
 ## Planned Breaking API Changes (25.0)
 
 ### Deprecated: `protocol.{register,intercept}{Buffer,String,Stream,File,Http}Protocol`