deleted trash bin from gprs grammar, cause we have waste bin

ps-grammar/gprs/gprs.jsgf

@@ -45,7 +45,6 @@ public <task> = [<robot_name>] [(would | could) you] [please] <command> [please]
 <table_class> = kitchen_table | hallway_table | dinner_table | couch_table ;
 <door_class> = (room door);
 <room_class> = kitchen | living_room | bedroom | hallway;
-<utensil_class> = trash_bin;
 <exit_class> = (exit door) | (entry door);
 
 <preposition> = into | to | from | on;