Remove kotlin-maven-plugin dependency.

Original Pull Request: #2866

Author: christophstrobl

pom.xml

@@ -127,12 +127,6 @@
 			<scope>test</scope>
 		</dependency>
 
-		<dependency>
-			<groupId>org.jetbrains.kotlin</groupId>
-			<artifactId>kotlin-maven-plugin</artifactId>
-			<version>${kotlin}</version>
-		</dependency>
-
 		<!--  RxJava -->
 
 		<dependency>