Drop support for RxJava 1.

Closes #1544

Author: mp911de

Diff for: parent/pom.xml

@@ -123,8 +123,6 @@
 		<mockk>1.12.2</mockk>
 		<querydsl>5.0.0</querydsl>
 		<reactor>2020.0.15-SNAPSHOT</reactor>
-		<rxjava>1.3.8</rxjava>
-		<rxjava-reactive-streams>1.2.1</rxjava-reactive-streams>
 		<rxjava2>2.2.21</rxjava2>
 		<rxjava3>3.1.3</rxjava3>
 		<smallrye-mutiny>1.3.0</smallrye-mutiny>