Update mill-scalafix to 0.4.0

Author: scala-steward

build.sc

@@ -1,5 +1,5 @@
 import $ivy.`com.goyeau::mill-git::0.2.4`
-import $ivy.`com.goyeau::mill-scalafix::0.3.2`
+import $ivy.`com.goyeau::mill-scalafix::0.4.0`
 import $ivy.`de.tototec::de.tobiasroeser.mill.integrationtest::0.7.1`
 import $ivy.`io.github.davidgregory084::mill-tpolecat::0.3.5`
 import com.goyeau.mill.git.{GitVersionModule, GitVersionedPublishModule}