Update japicmp configuration for 2.1.0

Author: Ron Liu

pom.xml

@@ -178,7 +178,7 @@ under the License.
 		<minikdc.version>3.2.4</minikdc.version>
 		<hive.version>2.3.10</hive.version>
 		<orc.version>1.5.6</orc.version>
-		<japicmp.referenceVersion>2.0.0</japicmp.referenceVersion>
+		<japicmp.referenceVersion>2.1.0</japicmp.referenceVersion>
 		<japicmp.outputDir>tools/japicmp-output</japicmp.outputDir>
 		<checkstyle.version>10.18.2</checkstyle.version>
 		<spotless.skip>false</spotless.skip>