Do not use projectTest helper to setup kotlinx-metadata-jvm

It sets up test instrumenter which cannot be used when running
these tests under JDK6.

Do not setup working dir, as there tests do not depend on it.

libraries/kotlinx-metadata/jvm/build.gradle.kts

@@ -79,6 +79,3 @@ if (deployVersion != null) {
     publish()
 }
 
-projectTest {
-    workingDir = rootDir
-}