Remove unnecessary setting

It was added mostly to make the coursier-based sbt launcher
(https://github.com/coursier/sbt-launcher) work a bit better

build.sbt

@@ -3,8 +3,6 @@ import Aliases._
 import Settings._
 import Publish._
 
-parallelExecution.in(Global) := false
-
 lazy val core = crossProject
   .disablePlugins(ScriptedPlugin)
   .jvmConfigure(_.enablePlugins(ShadingPlugin))