Released reactphp/async v4.3.0

[SimonFrings]

Released reactphp/async v4.3.0 today 🎉

• Feature: Improve performance by avoiding unneeded references in FiberMap.
  (#88 by @clue)

• Feature: Improve PHP 8.4+ support by avoiding implicitly nullable type declarations.
  (#87 by @clue)

• Improve type safety for test environment.
  (#86 by @SimonFrings)

– See https://github.com/reactphp/async/releases/tag/v4.3.0