Add 12-hour clock format setting to dconf configuration

dconf-settings.ini

@@ -1,3 +1,6 @@
+[/org/gtk/settings/file-chooser]
+clock-format='12h'
+
 [org/gnome/desktop/background]
 color-shading-type='solid'
 picture-options='zoom'
@@ -21,6 +24,7 @@ gtk-theme='adw-gtk3-dark'
 document-font-name='Adwaita Sans 11'
 #icon-theme='Yaru'
 monospace-font-name='Adwaita Mono 13'
+clock-format = '12h'
 
 [org/gnome/desktop/screensaver]
 color-shading-type='solid'