Update sbt-mima-plugin to 1.1.1 (#356)

Author: scala-steward

project/plugins.sbt

@@ -1,5 +1,5 @@
 addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.5.10")
-addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "1.1.0")
+addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "1.1.1")
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.11.0")
 addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.2.0")
 addSbtPlugin("org.scala-js" % "sbt-jsdependencies" % "1.0.2")