Bump vaadin-bom from 16.0.0 to 20.0.6#21

dependabot[bot] wants to merge 1 commit intomasterJava-Publications/show-vulnerabilities-vaadin-v16:masterfrom

dependabot/maven/com.vaadin-vaadin-bom-20.0.6Java-Publications/show-vulnerabilities-vaadin-v16:dependabot/maven/com.vaadin-vaadin-bom-20.0.6Copy head branch name to clipboard