Update 3.12.0.md

(cherry picked from commit b583889)

Conflicts:
	release-notes/3.12.0.md

Author: michaelklishin

release-notes/3.12.0.md

@@ -1,12 +1,6 @@
-<<<<<<< HEAD
-## RabbitMQ 3.12.0-rc.3
-
-RabbitMQ `3.12.0-rc.3` is a candidate of a new feature release.
-=======
 ## RabbitMQ 3.12.0
 
 RabbitMQ `3.12.0` is a new feature release.
->>>>>>> b583889e4f (Update 3.12.0.md)
 
 ## Highlights