Move OptionConvertersTest to JS-only test root

Author: haukeh

build.sbt

@@ -120,6 +120,7 @@ lazy val compat = new MultiScalaCrossProject(
       }
       Seq(s"$opt:$x->$y/")
     },
+    Test / unmanagedSourceDirectories += (ThisBuild / baseDirectory).value / "compat/src/test/scala-js",
     Compile / unmanagedSourceDirectories += {
       val jsParent = (ThisBuild / baseDirectory).value / "compat/js/src/main"
       CrossVersion.partialVersion(scalaVersion.value) match {

compat/src/test/scala-2.11_2.12/test/scala/jdk/OptionConvertersTest.scala renamed to compat/src/test/scala-js/test/scala/jdk/OptionConvertersTest.scala

@@ -8,7 +8,7 @@ import scala.jdk.OptionConverters._
 
 /**
  * The tests were copied from the Scala 2.13 Standard Library. `scala.jdk.javaapi` stuff has been omitted and
- * everything concerning `OptionalInt`, `OptionalDouble` and `OptionalLong` is only available on the jvm tests.
+ * everything concerning `OptionalInt`, `OptionalDouble` and `OptionalLong` is only available in the jvm tests.
  *
  * See https://github.com/scala/scala/blob/2.13.x/test/junit/scala/jdk/OptionConvertersTest.scala.
  */