Avoid pulling broken Maven artifact

I just created eclipse-archived/xtext-lib#146 with details.

Author: Blaisorblade

project/Build.scala

@@ -874,7 +874,8 @@ object Build {
       fork in run := true,
       fork in Test := true,
       libraryDependencies ++= Seq(
-        "org.eclipse.lsp4j" % "org.eclipse.lsp4j" % "0.5.0",
+        "org.eclipse.xtend" % "org.eclipse.xtend.lib" % "2.16.0",
+        "org.eclipse.lsp4j" % "org.eclipse.lsp4j" % "0.5.0" exclude ("org.eclipse.xtend", "org.eclipse.xtend.lib"),
         Dependencies.`jackson-databind`
       ),
       javaOptions := (javaOptions in `dotty-compiler-bootstrapped`).value,