Application: rely on Granite.StyleManager (#377)

Granite.StyleManager handles setting dark mode since 7.7.0

Author: danirabbit

README.md

@@ -16,7 +16,7 @@ You'll need the following dependencies:
 
 * libgee-0.8-dev
 * libglib2.0-dev (>= 2.76)
-* libgranite-7-dev
+* libgranite-7-dev (>= 7.7.0)
 * libgtk-4-dev
 * libadwaita-1-dev (>= 1.4)
 * meson (>= 0.57.0)

src/Application.vala

@@ -73,15 +73,6 @@ namespace Switchboard {
 
             Granite.init ();
 
-            var granite_settings = Granite.Settings.get_default ();
-            var gtk_settings = Gtk.Settings.get_default ();
-
-            gtk_settings.gtk_application_prefer_dark_theme = granite_settings.prefers_color_scheme == Granite.Settings.ColorScheme.DARK;
-
-            granite_settings.notify["prefers-color-scheme"].connect (() => {
-                gtk_settings.gtk_application_prefer_dark_theme = granite_settings.prefers_color_scheme == Granite.Settings.ColorScheme.DARK;
-            });
-
             var back_action = new SimpleAction ("back", null);
             var quit_action = new SimpleAction ("quit", null);
             var updates_action = new SimpleAction ("show-updates", null);