[Release 0.5.1] Update latest released version in README.adoc (#149)

diff --git a/README.adoc b/README.adoc
index 37de63a..6c630e4 100644
--- a/README.adoc
+++ b/README.adoc
@@ -19,7 +19,7 @@
 = Reactive client for Apache Pulsar
 
 :github: https://github.com/apache/pulsar-client-reactive
-:latest_version: 0.5.0
+:latest_version: 0.5.1
 
 Reactive client for Apache Pulsar which is compatible with the Reactive Streams specification.
 This uses Project Reactor as the Reactive Streams implementation.