Add changelog for 3.3.2-RC2

Author: Kordyjan

changelogs/3.3.2-RC2.md

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+# Backported fixes
+
+- Update Scala Library to 2.13.12 [#19454](https://github.com/lampepfl/dotty/pull/19454)
+- Fix expandParam's use of argForParam/isArgPrefixOf. [#19412](https://github.com/lampepfl/dotty/pull/19412)
+
+# Contributors
+
+Thank you to all the contributors who made this release possible 🎉
+
+According to `git shortlog -sn --no-merges 3.3.2-RC1..3.3.2-RC2` these are:
+
+```
+     2	Paweł Marks
+     1	Dale Wijnand
+     1	Jan Chyb
+     1	Nicolas Stucki
+     1	Seth Tisue
+
+
+```