Revert "Fix HelloWorld Samples (#1505)" (#1506)

This reverts commit 4915076.

Author: Lukasa

Sources/Examples/HelloWorld/Client/helloworldclient.swift renamed to Sources/Examples/HelloWorld/Client/main.swift

@@ -20,7 +20,6 @@ import HelloWorldModel
 import NIOCore
 import NIOPosix
 
-@main
 @available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
 struct HelloWorld: AsyncParsableCommand {
   @Option(help: "The port to connect to")

Sources/Examples/HelloWorld/Server/HelloWorldServer.swift renamed to Sources/Examples/HelloWorld/Server/main.swift

@@ -20,7 +20,6 @@ import HelloWorldModel
 import NIOCore
 import NIOPosix
 
-@main
 @available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
 struct HelloWorld: AsyncParsableCommand {
   @Option(help: "The port to listen on for new connections")