4.1.0 release notes: prepare for 4.1.0 GA

(cherry picked from commit cb4676d)

Conflicts:
	release-notes/4.1.0.md

Author: michaelklishin

release-notes/4.1.0.md

@@ -1,6 +1,6 @@
-## RabbitMQ 4.1.0-rc.1
+## RabbitMQ 4.1.0
 
-RabbitMQ 4.1.0-rc.1 is a candidate of a new feature release.
+RabbitMQ 4.1.0 is a new feature release.
 
 See Compatibility Notes below to learn about **breaking or potentially breaking changes** in this release.