Backport PR matplotlib#29035: FIX: Don't set_wmclass on GTK3

Author: greglucas

lib/matplotlib/backends/_backend_gtk.py

@@ -143,7 +143,6 @@ def __init__(self, canvas, num):
         super().__init__(canvas, num)
 
         if gtk_ver == 3:
-            self.window.set_wmclass("matplotlib", "Matplotlib")
             icon_ext = "png" if sys.platform == "win32" else "svg"
             self.window.set_icon_from_file(
                 str(cbook._get_data_path(f"images/matplotlib.{icon_ext}")))