Update gitbucket to 4.39.0

Author: scala-steward-bot

build.sbt

@@ -2,7 +2,7 @@ organization := "io.github.gitbucket"
 name := "gitbucket-gist-plugin"
 version := "4.22.0"
 scalaVersion := "2.13.10"
-gitbucketVersion := "4.38.4"
+gitbucketVersion := "4.39.0"
 
 scalacOptions := Seq("-deprecation", "-feature", "-language:postfixOps")
 Compile / javacOptions ++= Seq("-target", "8", "-source", "8")