phone: Drop LIBGL_ALWAYS_SOFTWARE

This was used to get kitty to work however GNOME terminal is much faster
than kitty on the PinePhone and has touch support, making it superior
for daily use.

hosts/phone/configuration.nix

@@ -49,12 +49,6 @@ in
     };
   };
 
-  environment = {
-    sessionVariables = {
-      LIBGL_ALWAYS_SOFTWARE = "true";
-    };
-  };
-
   programs = {
     calls.enable = true;
   };