Update release notes

Signed-off-by: cwasicki <126617870+cwasicki@users.noreply.github.com>

Author: cwasicki

RELEASE_NOTES.md

@@ -6,7 +6,7 @@
 
 ## Upgrading
 
-<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
+* Updates `black` to version 26.3.1, which fixes a security issue.
 
 ## New Features