[gnome-music/wip/jfelder/about-dialog] aboutdialog: Port to Gtk4

[Jean Felder <jfelder src gnome org>]

commit 90cca7d70645bae9b815c200745132e6d4481311
Author: Jean Felder <jfelder src gnome org>
Date:   Fri Feb 18 00:14:31 2022 +0100

    aboutdialog: Port to Gtk4
    
    The response signal does not exist anymore. It has been replaced by
    "close-request". Also, it is now useless to listen to
    "close-request" because the dialog is automatically destroyed on
    close.
    
    Close: #502

 gnomemusic/widgets/aboutdialog.py | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)
---
diff --git a/gnomemusic/widgets/aboutdialog.py b/gnomemusic/widgets/aboutdialog.py
index ac8b20e20..51b720912 100644
--- a/gnomemusic/widgets/aboutdialog.py
+++ b/gnomemusic/widgets/aboutdialog.py
@@ -22,6 +22,8 @@
 # code, but you are not obligated to do so.  If you do not wish to do so,
 # delete this exception statement from your version.
 
+from __future__ import annotations
+
 from gi.repository import Gtk
 
 
@@ -33,8 +35,3 @@ class AboutDialog(Gtk.AboutDialog):
 
     def __init__(self):
         super().__init__()
-
-        self.connect("response", self._about_response)
-
-    def _about_response(self, klass, data=None):
-        klass.destroy()