Update process_execute function comment to reflect new function arguments

src/userprog/process.c

@@ -49,8 +49,8 @@ struct process_start_data
 static thread_func start_process NO_RETURN;
 static bool load (const char *cmdline, void (**eip) (void), void **esp);
 
-/* Starts a new thread running a user program loaded from
-   FILENAME.  The new thread may be scheduled (and may even exit)
+/* Starts a new thread running a user program executed via
+   CMD.  The new thread may be scheduled (and may even exit)
    before process_execute() returns.  Returns the new process's
    thread id, or TID_ERROR if the thread cannot be created. */
 tid_t