docs: fix casing of _Deprecated_ (#39152)

docs/api/system-preferences.md

@@ -297,7 +297,7 @@ This API is only available on macOS 10.14 Mojave or newer.
     * `window-frame` - Window frame.
     * `window-text` - Text in windows.
   * On **macOS**
-    * `alternate-selected-control-text` - The text on a selected surface in a list or table. _deprecated_
+    * `alternate-selected-control-text` - The text on a selected surface in a list or table. _Deprecated_
     * `control-background` - The background of a large interface element, such as a browser or table.
     * `control` - The surface of a control.
     * `control-text` -The text of a control that isn’t disabled.