Update fcntl doc: replace IOError with OSError

Issue #26716. IOError is a deprecated alias to OSError since Python 3.3.
diff --git a/Modules/fcntlmodule.c b/Modules/fcntlmodule.c
index 97ff07c..e61c930 100644
--- a/Modules/fcntlmodule.c
+++ b/Modules/fcntlmodule.c
@@ -344,7 +344,7 @@
 
 When operation is LOCK_SH or LOCK_EX, it can also be bitwise ORed with
 LOCK_NB to avoid blocking on lock acquisition.  If LOCK_NB is used and the
-lock cannot be acquired, an IOError will be raised and the exception will
+lock cannot be acquired, an OSError will be raised and the exception will
 have an errno attribute set to EACCES or EAGAIN (depending on the operating
 system -- for portability, check for either value).