Add changelog for 3.5.2-RC2

Author: WojciechMazur

changelogs/3.5.2-RC2.md

@@ -0,0 +1,14 @@
+# Backported fixes
+
+- Revert pattern matching improvements introducing regressions in 3.5.2 [#21734](https://github.com/lampepfl/dotty/pull/21734)
+
+# Contributors
+
+Thank you to all the contributors who made this release possible 🎉
+
+According to `git shortlog -sn --no-merges 3.5.2-RC1..3.5.2-RC2` these are:
+
+```
+     4  Wojciech Mazur
+     1  Dale Wijnand
+```