gnome-shell: Drop app-well-menu style class

Based on upstream commit:
https://gitlab.gnome.org/GNOME/gnome-shell/-/commit/b496c9f956f6da7e72b585e58ac20cad51f64e54

Author: jnsh

common/gnome-shell/41/sass/_common.scss

@@ -1009,8 +1009,7 @@ StScrollBar {
   spacing: 4px;
 }
 
-.app-menu,
-.app-well-menu {
+.app-menu {
   max-width: 27.25em;
 }