Remove duplicate dependencies. (#15135)

Author: wuwen5

dubbo-rpc/dubbo-rpc-triple/pom.xml

@@ -129,12 +129,6 @@
       <version>${project.parent.version}</version>
       <optional>true</optional>
     </dependency>
-    <dependency>
-      <groupId>org.apache.dubbo</groupId>
-      <artifactId>dubbo-cluster</artifactId>
-      <version>${project.parent.version}</version>
-      <scope>test</scope>
-    </dependency>
   </dependencies>
   <build>
     <plugins>