Mention Bug Fix in release notes

A buffer overrun in the code to determine
which files need to be marked as hidden [was
plugged](git-for-windows/git#2371).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

ReleaseNotes.md

@@ -53,6 +53,7 @@ Note! As a consequence of making `git config --system` work as expected, the loc
 * The installer's "ProductVersion" [is now consistent with older Git for Windows versions'](https://github.com/git-for-windows/build-extra/pull/257).
 * [Makes `git config --system` work like you think it should](https://github.com/git-for-windows/git/pull/2358).
 * The (still experimental) built-in `git add -p` [no longer gets confused about incomplete lines](https://github.com/git-for-windows/git/pull/2368) (i.e. a file's l last line that does not end in a Line Feed).
+* A buffer overrun in the code to determine which files need to be marked as hidden [was plugged](https://github.com/git-for-windows/git/pull/2371).
 
 ## Changes since Git for Windows v2.22.0 (June 8th 2019)