#14863: Update the documentation of os.fdopen()

There's no bufsize argument anymore, and os.fdopen() is only a very
thin wrapper around open() anymore. Change the documentation to
reflect that.
diff --git a/Misc/NEWS b/Misc/NEWS
index d9b8b5c..efec480 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -67,6 +67,9 @@
 Library
 -------
 
+- Issue #14863: Update the documentation of os.fdopen() to reflect the
+  fact that it's only a thin wrapper around open() anymore.
+
 - Issue #14036: Add an additional check to validate that port in urlparse does
   not go in illegal range and returns None.