Fix vertx-web-5.0

Author: smola

dd-java-agent/instrumentation/vertx-web-5.0/build.gradle

@@ -1,5 +1,7 @@
 // Set properties before any plugins get loaded
 ext {
+  defaultJdkVersion = 11
+  defaultJavaVersion = 8
   minJavaVersionForTests = JavaVersion.VERSION_11
 }
 
@@ -22,12 +24,6 @@ configurations {
   testArtifacts
 }
 
-java {
-  toolchain {
-    languageVersion.set(JavaLanguageVersion.of(11))
-  }
-}
-
 // Create test artifacts so vertx-rx can reuse the server test instrumentation and base class
 artifacts {
   testArtifacts testJar