update UnmooredDocComment test

sbt-test/UnmooredDocComment/test-1/build.sbt

@@ -1,10 +1,8 @@
 ThisBuild / scalafixDependencies += "com.github.xuwei-k" %% "scalafix-rules" % sys.props("scalafix-rules.version")
 
 TaskKey[Unit]("check") := {
-  if(!scala.util.Properties.isWin) {
-    val actual = "target/warnings/warnings.json"
-    val expect = "expect.json"
-    sys.process.Process(Seq("diff", actual, expect)).!
-    assert(IO.read(file(actual)) == IO.read(file(expect)))
-  }
+  def f(x: String) = JsonParser.parse(IO.read(file(x))).fold(sys.error(_), identity)
+  val actual = f("target/warnings/warnings.json")
+  val expect = f("expect.json")
+  assert(actual == expect, s"${actual} != ${expect}")
 }

sbt-test/UnmooredDocComment/test-1/project/plugins.sbt

@@ -1,2 +1,3 @@
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % sys.props("scalafix.version"))
 addSbtPlugin("com.github.xuwei-k" % "warning-diff-scalafix-plugin" % "0.6.0")
+libraryDependencies += "io.github.argonaut-io" %% "argonaut" % "6.3.11"