Merge pull request #15930 from rabbitmq/mk-correct-4.3.0-release-notes

`4.3.0` release notes: finish a sentence

Author: michaelklishin

release-notes/4.3.0.md

@@ -8,7 +8,8 @@ RabbitMQ `4.3.0-rc.1` is a new feature release candidate.
 ### Mnesia and Parition Handling Strategies are Removed
 
 Since only `4.2.x` clusters can upgrade to `4.3.0` [in place](https://www.rabbitmq.com/docs/upgrade), this
-won't be a breaking change for nearly all instalations but
+won't be a breaking change for nearly all instalations but it will affect community
+plugins that use Mnesia.
 
 All partition handling-related keys in `rabbitmq.conf` will be
 accepted by `4.3.0` nodes but won't have any effect: