Update build.mill

Author: lihaoyi

build.mill

@@ -4,7 +4,7 @@
 package build
 
 import mill._, scalalib._, scalajslib._, scalanativelib._, publish._
-import mill.main.VcsVersion
+import mill.vcs.VcsVersion
 import com.github.lolgab.mill.mima._
 
 val dottyCommunityBuildVersion = sys.props.get("dottyVersion").toList