One more tweak to 4.1.0-rc.1 release notes

(cherry picked from commit 5a9482d)

Author: michaelklishin

release-notes/4.1.0.md

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