Mention Bug Fix in release notes

When cloning into an existing (empty)
directory fails, [Git no longer removes said
directory](git-for-windows/git#1421).

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

ReleaseNotes.md

@@ -45,6 +45,10 @@ Git for Windows now has a new homepage: [https://gitforwindows.org/](https://git
 * `git checkout` [is now a lot faster when checking out a *lot* of files](https://github.com/git-for-windows/git/pull/1419).
 * The `core.excludesfile` [can now reference a symbolic link](https://github.com/git-for-windows/git/issues/1392).
 
+### Bug Fixes
+
+* When cloning into an existing (empty) directory fails, [Git no longer removes said directory](https://github.com/git-for-windows/git/pull/1421).
+
 ## Changes since Git for Windows v2.15.1 (November 29th 2017)
 
 ### Bug Fixes