Update sbt-tpolecat to 0.1.20 (#2159)

Author: scala-steward

project/plugins.sbt

@@ -7,7 +7,7 @@ addSbtPlugin("com.github.cb372" % "sbt-explicit-dependencies" % "0.2.16")
 addSbtPlugin("com.github.tkawachi" % "sbt-doctest" % "0.9.9")
 addSbtPlugin("com.typesafe.sbt" % "sbt-native-packager" % "1.8.1")
 addSbtPlugin("de.heikoseeberger" % "sbt-header" % "5.6.0")
-addSbtPlugin("io.github.davidgregory084" % "sbt-tpolecat" % "0.1.19")
+addSbtPlugin("io.github.davidgregory084" % "sbt-tpolecat" % "0.1.20")
 addSbtPlugin("pl.project13.scala" % "sbt-jmh" % "0.4.2")
 addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.0.0")
 addSbtPlugin("org.scoverage" % "sbt-scoverage" % "1.8.2")