Upgrade to Rxjava 1.3.4

Closes gh-11098

spring-boot-project/spring-boot-dependencies/pom.xml

@@ -130,7 +130,7 @@
 		<reactor-bom.version>Bismuth-SR4</reactor-bom.version>
 		<rest-assured.version>3.0.5</rest-assured.version>
 		<reactive-streams.version>1.0.1</reactive-streams.version>
-		<rxjava.version>1.3.3</rxjava.version>
+		<rxjava.version>1.3.4</rxjava.version>
 		<rxjava-adapter.version>1.2.1</rxjava-adapter.version>
 		<rxjava2.version>2.1.6</rxjava2.version>
 		<selenium.version>3.7.1</selenium.version>