zed-editor: fix darwin build by adding runtime_shaders to checkFeatures (#490957)

  # Some crates define extra types or enum values in test configuration which then lead

  # to type checking errors in other crates unless this feature is enabled.

  checkFeatures = [ "visual-tests" ];

  # gpui/runtime_shaders is required on darwin for the same reason as buildFeatures above:

  # without it, build.rs invokes the proprietary Metal shader compiler.

  checkFeatures = [

    "visual-tests"

  ]

  ++ finalAttrs.buildFeatures;

  env = {

    ALLOW_MISSING_LICENSES = true;