Incorrect `Left` and `Right` class definition

[klimick]

Current definitions for Right and Left is incorrect:

/**
 * @template-covariant L
 * @template-covariant R
 * @psalm-immutable
 * @extends Either<L, R>
 */
final class Right extends Either { ... }

/**
 * @template-covariant L
 * @template-covariant R
 * @psalm-immutable
 * @extends Either<L, R>
 */
final class Left extends Either { ... }

Should be:

/**
 * @template-covariant R
 * @psalm-immutable
 * @extends Either<empty, R>
 */
final class Right extends Either { ... }

/**
 * @template-covariant L
 * @psalm-immutable
 * @extends Either<L, empty>
 */
final class Left extends Either { ... }