test: update javassist for Java 16+ support

See vaadin/testbench#1288

Author: javier-godoy

pom.xml

@@ -137,6 +137,13 @@
 	        <version>4.3.1</version>
 	    	<scope>test</scope>
     	</dependency>
+    	<dependency>
+            <!--  https://github.com/vaadin/testbench/pull/1288 -->
+            <groupId>org.javassist</groupId>
+            <artifactId>javassist</artifactId>
+            <version>3.27.0-GA</version>
+            <scope>test</scope>
+        </dependency>
 		<dependency>
 			<groupId>com.flowingcode.vaadin.addons.demo</groupId>
 			<artifactId>commons-demo</artifactId>