Explore the sbt documentation to understand which method(s) you need to use to prevent downloading the transitive dependency "org.slf4j" % "slf4j-api" because it is already defined.
libraryDependencies ++= Seq(
"org.slf4j" % "slf4j-api" % "1.7.30",
("org.eclipse.jetty" % "jetty-server" % JettyVersion)._____("org.slf4j", "slf4j-api"),
("org.eclipse.jetty" % "jetty-servlet" % JettyVersion)._____("org.slf4j", "slf4j-api")
)