Upgrade to RxJava 2.2.21.

See #1350

Author: mp911de

parent/pom.xml

@@ -119,7 +119,7 @@
 		<reactor>Dysprosium-SR15</reactor>
 		<rxjava>1.3.8</rxjava>
 		<rxjava-reactive-streams>1.2.1</rxjava-reactive-streams>
-		<rxjava2>2.2.20</rxjava2>
+		<rxjava2>2.2.21</rxjava2>
 		<slf4j>1.7.26</slf4j>
 		<spring>5.2.12.RELEASE</spring>
 		<spring-hateoas>1.0.5.RELEASE</spring-hateoas>