Revert "trace2:data: add trace2 sub-process classification"

This reverts commit a1ab077.

Author: jeffhostetler

sub-process.c

@@ -88,7 +88,6 @@ int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, co
 	process->out = -1;
 	process->clean_on_exit = 1;
 	process->clean_on_exit_handler = subprocess_exit_handler;
-	process->trace2_child_class = "subprocess";
 
 	err = start_command(process);
 	if (err) {