Ruby: Add change note

Author: hmac

ruby/ql/lib/change-notes/2022-08-05-active-record-associations.md

@@ -0,0 +1,6 @@
+---
+category: minorAnalysis
+---
+* Calls to methods generated by ActiveRecord associations are now recognised as
+  instantiations of ActiveRecord objects. This increases the sensitivity of
+  queries such as `rb/sql-injection` and `rb/stored-xss`.