various: remove elementary-icon-theme from buildInputs

These apps don't hardcode their icon themes and the icon theme
is no longer picked up by wrapGAppsHook by default. User may
also able to choose to use icon themes of their choice so pulling
them to XDG_DATA_DIRS is mostly no use.

pkgs/applications/audio/vocal/default.nix

···
     libgee
     libnotify
     libunity
-    pantheon.elementary-icon-theme
     pantheon.granite
     sqlite
     webkitgtk

pkgs/applications/misc/regextester/default.nix

···
   ];
 
   buildInputs = [
-    pantheon.elementary-icon-theme
     pantheon.granite
     glib
     libgee

pkgs/applications/office/bookworm/default.nix

···
   ];
 
   buildInputs = [
-    pantheon.elementary-icon-theme
     pantheon.granite
     glib
     libgee

pkgs/applications/office/spice-up/default.nix

···
     libgee
     libgudev
     libsoup
-    pantheon.elementary-icon-theme
     pantheon.granite
   ];
 

pkgs/applications/science/math/nasc/default.nix

···
     gtk3
     gtksourceview
     libgee
-    pantheon.elementary-icon-theme
     pantheon.granite
     webkitgtk
     # We add libqalculate's runtime dependencies because nasc has it as a modified subproject.

pkgs/tools/misc/hashit/default.nix

···
   buildInputs = [
     gtk3
     libgee
-    pantheon.elementary-icon-theme
     pantheon.granite
   ];
 

pkgs/tools/text/snippetpixie/default.nix

···
     xorg.libXtst
     pantheon.granite
     pantheon.elementary-gtk-theme
-    pantheon.elementary-icon-theme
   ];
 
   doCheck = true;