Doc nits for bpo-16500 (#1841)

* Doc nits for bpo-16500

* Fix more references
diff --git a/Python/thread.c b/Python/thread.c
index 8fa978a..ed697ac 100644
--- a/Python/thread.c
+++ b/Python/thread.c
@@ -325,7 +325,7 @@
 }
 
 /* Forget everything not associated with the current thread id.
- * This function is called from PyOS_AfterFork().  It is necessary
+ * This function is called from PyOS_AfterFork_Child().  It is necessary
  * because other thread ids which were in use at the time of the fork
  * may be reused for new threads created in the forked process.
  */