Bump jetty-server from 9.3.1.v20150714 to 9.4.21.v20190926#31

dependabot-preview[bot] wants to merge 1 commit intomasterTeam-IO/Launcher:masterfrom

dependabot/gradle/org.eclipse.jetty-jetty-server-9.4.21.v20190926Team-IO/Launcher:dependabot/gradle/org.eclipse.jetty-jetty-server-9.4.21.v20190926Copy head branch name to clipboard