Update sbt-mima-plugin to 0.6.4 (#84)

Author: scala-steward

build.sbt

@@ -6,6 +6,6 @@ licenses            := Seq(("Apache-2.0", url("https://www.apache.org/licenses/L
 
 addSbtPlugin("com.typesafe.sbt" % "sbt-osgi" % "0.9.5")
 addSbtPlugin("de.heikoseeberger" % "sbt-header" % "5.4.0")
-addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.6.3")
+addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.6.4")
 addSbtPlugin("com.dwijnand" % "sbt-travisci" % "1.2.0")   // set scalaVersion and crossScalaVersions
 addSbtPlugin("com.geirsson" % "sbt-ci-release" % "1.5.0") // set version, scmInfo, publishing settings