Bump vaadin.version from 8.1.6 to 13.0.1

Bumps `vaadin.version` from 8.1.6 to 13.0.1.

Updates `vaadin-bom` from 8.1.6 to 13.0.1

Updates `vaadin-maven-plugin` from 8.1.6 to 13.0.1
- [Release notes](https://github.com/vaadin/platform/releases)
- [Commits](https://github.com/vaadin/platform/commits/13.0.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Author: dependabot-support

chat-example/chat-vaadin-client/pom.xml

@@ -23,7 +23,7 @@
     <maven.compiler.target>1.8</maven.compiler.target>
 
     <jetty.plugin.version>9.4.15.v20190215</jetty.plugin.version>
-    <vaadin.version>8.1.6</vaadin.version>
+    <vaadin.version>13.0.1</vaadin.version>
     <!-- If there are no local customisations, this can also be "fetch" or "cdn" -->
     <vaadin.widgetset.mode>cdn</vaadin.widgetset.mode>
   </properties>