gh-116738: Fix typo

Author: yoney

Lib/test/test_free_threading/test_heapq.py

@@ -236,7 +236,7 @@ def run_concurrently(self, worker_func, args, nthreads) -> None:
         barrier = Barrier(nthreads)
 
         def wrapper_func(*args):
-            # Wait for all threadss to reach this point before proceeding.
+            # Wait for all threads to reach this point before proceeding.
             barrier.wait()
             worker_func(*args)