doc: Add missing PR 16333 release note

Author: MarcoFalke

doc/release-notes.md

@@ -108,8 +108,10 @@ RPC
 Tests
 -----
 
-- For the `regtest` network the BIP 66 (DERSIG) activation height was changed
-  from 1251 to 102. (#22632)
+- For the `regtest` network the activation heights of several softforks were
+  changed.
+  * BIP 34 (blockheight in coinbase) from 500 to 2 (#16333)
+  * BIP 66 (DERSIG) from 1251 to 102 (#22632)
 
 Credits
 =======