Update pekko-actor, pekko-slf4j, ... to 1.4.0

Author: scala-steward

build.sbt

@@ -21,7 +21,7 @@ lazy val treehub = (project in file("."))
   .settings(UnitTest / testOptions := Seq(Tests.Filter(unitFilter)))
   .settings(IntegrationTest / testOptions := Seq(Tests.Filter(itFilter)))
   .settings(Seq(libraryDependencies ++= {
-    val pekkoV = "1.1.5"
+    val pekkoV = "1.4.0"
     val pekkoHttpV = "1.2.0"
     val scalaTestV = "3.0.9"
     val libatsV = "5.0.0"