Clean up mill process in LauncherOldVersionTests to prevent test report failures

blog/modules/ROOT/pages/5-executable-jars.adoc

@@ -34,7 +34,7 @@ other build tools and toolchains will be able to provide the same convenience
 
 // end::header[]
 
-## Trying Out Mill's Executable Assmeblies
+## Trying Out Mill's Executable Assemblies
 
 To try out Mill's executable assembly jars, you can reproduce the above steps
 with the following code and config:

integration/feature/launcher-old-versions/src/LauncherOldVersionsTests.scala

@@ -26,6 +26,8 @@ class LauncherOldVersionsTests(version: String) extends UtestIntegrationTestSuit
       val res = os.call(cmd = (launcherScript, "version"), cwd = workspacePath, stderr = os.Pipe)
       val outText = res.out.text().trim
       assert(outText == version)
+      os.call(cmd = (launcherScript, "shutdown"), cwd = workspacePath, check = false)
+      os.remove.all(workspacePath / "out")
     }
   }
 }