bump: sbt-scalafmt 2.5.6 (was 2.5.5) (#664)

Author: scala-steward

project/plugins.sbt

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-addSbtPlugin("org.scalameta"         % "sbt-scalafmt"                       % "2.5.5")
+addSbtPlugin("org.scalameta"         % "sbt-scalafmt"                       % "2.5.6")
 addSbtPlugin("de.heikoseeberger"     % "sbt-header"                         % "5.10.0")
 addSbtPlugin("com.lightbend.paradox" % "sbt-paradox"                        % "0.10.7")
 addSbtPlugin("com.lightbend.paradox" % "sbt-paradox-lightbend-project-info" % "3.0.1")