Update sbt-docker to 1.6.0 (#145)

Author: scala-steward

project/plugins.sbt

@@ -1,6 +1,6 @@
 addSbtPlugin("com.typesafe.sbt"     % "sbt-native-packager"      % "1.7.3")
 addSbtPlugin("com.eed3si9n"         % "sbt-assembly"             % "0.15.0")
-addSbtPlugin("se.marcuslonnberg"    % "sbt-docker"               % "1.5.0")
+addSbtPlugin("se.marcuslonnberg"    % "sbt-docker"               % "1.6.0")
 addSbtPlugin("com.eed3si9n"         % "sbt-buildinfo"            % "0.9.0")
 addSbtPlugin("com.geirsson"         % "sbt-ci-release"           % "1.5.3")
 addSbtPlugin("org.scalameta"        % "sbt-scalafmt"             % "2.4.0")