Fix REPL runner (#3624)

`main` method is now special because it is trully static i.e. no
implicit `self` is being generated for it.
But since REPL's `main` isn't called `main` its invocation was missing
an argument.

Follow up on https://github.com/enso-org/enso/pull/3569

# Important Notes
Will work on adding a CI test for REPL to avoid problems with REPL in a
follow up PR.

engine/runner/src/main/scala/org/enso/runner/Main.scala

@@ -756,7 +756,10 @@ object Main {
       val mainCons = mainModule.getAssociatedConstructor
       val mainFun  = mainModule.getMethod(mainCons, mainMethodName)
       mainFun match {
-        case Some(main) => main.execute()
+        case Some(main) if mainMethodName != "main" =>
+          main.execute(mainCons.newInstance())
+        case Some(main) =>
+          main.execute()
         case None =>
           err.println(
             s"The module ${mainModule.getName} does not contain a `main` " +