improve racy test: scalafixAll was triggering Compile/compile

Through Test/scalafix & then Test/internalDependencyClasspath,
scalafixAll evaluates Compile/compile, which could make
Compile/scalafix run as expected sometimes before the fix in
68b7e82.

src/sbt-test/sbt-scalafix/wrapper/project/LintAllPlugin.scala

@@ -17,7 +17,7 @@ object LintAllPlugin extends AutoPlugin {
  override def projectSettings: Seq[Def.Setting[_]] =
  Seq(
  lintAll := {
- scalafixAll.toTask(" --check").value
+ scalafix.in(Compile).toTask(" --check").value
  // & other linters...
  }
  )