Fix plugin test.

Author: wu-sheng

test/plugin/pom.xml

@@ -38,6 +38,7 @@
         <java.version>8</java.version>
         <maven.compiler.source>${java.version}</maven.compiler.source>
         <maven.compiler.target>${java.version}</maven.compiler.target>
+        <maven.compiler.release>${java.version}</maven.compiler.release>
 
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>