Bump vaadin-bom from 13.0.5 to 14.6.8

Bumps vaadin-bom from 13.0.5 to 14.6.8.

---
updated-dependencies:
- dependency-name: com.vaadin:vaadin-bom
  dependency-type: direct:production
...

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

pom.xml

@@ -16,7 +16,7 @@
 
     <properties>
         <java.version>1.8</java.version>
-        <vaadin.version>13.0.13</vaadin.version>
+        <vaadin.version>14.6.8</vaadin.version>
         <card.version>0.9.4</card.version>
     </properties>