Do not withhold emission in pauseWhen

[SystemFw]

pauseWhen should emit elements as soon as it wakes up, instead of checking for the need to pause again.

The difference in behaviour came up when I was implementing this (very complex) combinator for a user, which alternates between two streams upon a timeout.

def switchRepeat[A](
    every: FiniteDuration,
    to: Stream[IO, A]
): Pipe[IO, A, A] = { in =>
  Stream.eval(SignallingRef.of[IO, Boolean](true)).flatMap { paused =>
    val pause = Pull.eval(paused.set(true))
    val unpause = Pull.eval(paused.set(false))

    def go(p: Pull.Timed[IO, A]): Pull[IO, A, Unit] =
      p.timeout(every) >> p.uncons.flatMap {
        case Some((Right(elems), next)) =>
          pause >> Pull.output(elems) >> go(next)
        case Some((Left(_), next)) =>
          unpause >> go(next)
        case None =>
          Pull.done
      }

    val foreground = in.pull.timed(go).stream
    val background = to.through(pauseWhen(paused))

    foreground.mergeHaltL(background)
  }
}

Given how complex the example is, and how hard it is to engineer alternative code that would trigger a difference in behaviour between the new and old implementation of pauseWhen, I haven't added a test covering my change. Let me know if you want me to try harder finding a minimised test