gnome-shell: Remove spacing between panelActivities and appMenu

As with upstream [1], the spacing seems exessive, and is
inconsistent with the buttons on the opposite side of the panel.

[1] https://gitlab.gnome.org/GNOME/gnome-shell/-/commit/b2a5417c3e68b9b7ed4c99220dedcf2483e5ebb0

common/gnome-shell/40/sass/_common.scss

@@ -873,10 +873,6 @@ StScrollBar {
     }
   }
 
-  #panelLeft, #panelCenter { // spacing between activities<>app menu and such
-    spacing: 8px;
-  }
-
   .panel-corner {
     -panel-corner-radius: $panel-corner-radius;
     -panel-corner-background-color: transparentize(black, 1);