Bump vaadin.version from 8.7.1 to 8.12.4 in /server#18

dependabot[bot] wants to merge 1 commit intomastervaadin/charts-tutorial:masterfrom

dependabot/maven/server/vaadin.version-8.12.4vaadin/charts-tutorial:dependabot/maven/server/vaadin.version-8.12.4Copy head branch name to clipboard