Fix typo in NEWS item about IDLE (os.flush() should be os.fsync()) (#13284)

diff --git a/Misc/NEWS.d/next/IDLE/2019-05-05-16-27-53.bpo-13102.AGNWYJ.rst b/Misc/NEWS.d/next/IDLE/2019-05-05-16-27-53.bpo-13102.AGNWYJ.rst
index 18b31b1..2a905bf 100644
--- a/Misc/NEWS.d/next/IDLE/2019-05-05-16-27-53.bpo-13102.AGNWYJ.rst
+++ b/Misc/NEWS.d/next/IDLE/2019-05-05-16-27-53.bpo-13102.AGNWYJ.rst
@@ -1 +1 @@
-When saving a file, call os.flush() so bits are flushed to e.g. USB drive.
+When saving a file, call os.fsync() so bits are flushed to e.g. USB drive.