Update sbt-mima-plugin to 1.1.6 (#1762)

Author: scala-steward

project/plugins.sbt

@@ -13,4 +13,4 @@ libraryDependencies += "jline" % "jline" % "2.14.6"
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.6.0")
 
 // binary compatibility checks
-addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "1.1.4")
+addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "1.1.6")