Update Reactive Pulsar Client 0.4.0 (#468)

Author: onobc

gradle.properties

@@ -5,7 +5,7 @@ org.gradle.parallel=true
 org.gradle.jvmargs=-Xmx4g -XX:+HeapDumpOnOutOfMemoryError -XX:+UseParallelGC -Dfile.encoding=UTF-8
 
 pulsarClientVersion=3.1.0
-pulsarClientReactiveVersion=0.3.0
+pulsarClientReactiveVersion=0.4.0
 springFrameworkVersion=6.1.0-M5
 
 # only used by docs, tests, and samples (unpublished deps)