Bump vaadin.version from 8.9.0 to 8.12.4 in /filedroptarget-and-selector-addon#3

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dependabot/maven/filedroptarget-and-selector-addon/vaadin.version-8.12.4gerald24/FileDropTargetAndSelector:dependabot/maven/filedroptarget-and-selector-addon/vaadin.version-8.12.4Copy head branch name to clipboard