Remove sbt-partial-unification (#3217)

* Replace partial-unification sbt plugin

* Remove unused sbt plugin

* Set -Ypartial-unification on binCompatTest project

build.sbt

@@ -633,7 +633,8 @@ lazy val binCompatTest = project
     useCoursier := false,
     commonScalaVersionSettings,
     addCompilerPlugin(("org.typelevel" %% "kind-projector" % kindProjectorVersion).cross(CrossVersion.full)),
-    libraryDependencies += mimaPrevious("cats-core", scalaVersion.value, version.value).last % Provided
+    libraryDependencies += mimaPrevious("cats-core", scalaVersion.value, version.value).last % Provided,
+    scalacOptions ++= (if (priorTo2_13(scalaVersion.value)) Seq("-Ypartial-unification") else Nil)
   )
   .settings(testingDependencies)
   .dependsOn(core.jvm % Test)
@@ -802,6 +803,7 @@ def commonScalacOptions(scalaVersion: String) =
   ) ++ (if (priorTo2_13(scalaVersion))
           Seq(
             "-Yno-adapted-args",
+            "-Ypartial-unification",
             "-Xfuture"
           )
         else

project/plugins.sbt

@@ -8,7 +8,6 @@ addSbtPlugin("com.typesafe.sbt" % "sbt-git" % "1.0.0")
 addSbtPlugin("com.github.tkawachi" % "sbt-doctest" % "0.9.5")
 addSbtPlugin("org.xerial.sbt" % "sbt-sonatype" % "3.8.1")
 addSbtPlugin("com.47deg" % "sbt-microsites" % "0.9.7")
-addSbtPlugin("org.lyranthe.sbt" % "partial-unification" % "1.1.2")
 addSbtPlugin("org.tpolecat" % "tut-plugin" % "0.6.13")
 addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "0.6.1")
 addSbtPlugin("org.portable-scala" % "sbt-scala-native-crossproject" % "0.6.1")

scalafix/project/plugins.sbt

@@ -1,2 +1 @@
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.11")
-addSbtPlugin("org.lyranthe.sbt" % "partial-unification" % "1.1.2")