BLI_task: fix bad freeing of current task_thread in case POSIX thread creation fails.

Trying to MEM_free a single item of a whole MEM_calloc'ated array, tsst...
Luckily looks like POSIX thread creation does not fail often! :P

source/blender/blenlib/intern/task.c

@@ -207,7 +207,6 @@ TaskScheduler *BLI_task_scheduler_create(int num_threads)
 
 			if (pthread_create(&scheduler->threads[i], NULL, task_scheduler_thread_run, thread) != 0) {
 				fprintf(stderr, "TaskScheduler failed to launch thread %d/%d\n", i, num_threads);
-				MEM_freeN(thread);
 			}
 		}
 	}