Update docs.

Build/MQTTnet.nuspec

@@ -17,7 +17,6 @@
 * [ManagedClient] Refactored log messages (thanks to @cstichlberger).
 * [Server] Added support for assigned client IDs (MQTTv5 only) (thanks to @bcrosnier).
 * [Server] Added interceptor for unsubscriptions.
-* [Server] Added support for direct specification of X502 certificates instead of byte arrays (BREAKING CHANGE! thanks to @stepkillah).
 * [MQTTnet.Server] Added interceptor for unsubscriptions.
     </releaseNotes>
     <copyright>Copyright Christian Kratky 2016-2019</copyright>