chore: Test 3.3.4-RC1

[He-Pin]

Motivation:
Test with 3.3.4-RC1

[He-Pin]

@WojciechMazur Why it now reports:

[error] -- [E030] Match case Unreachable Error: /home/runner/work/pekko/pekko/stream/src/main/scala/org/apache/pekko/stream/scaladsl/Flow.scala:3132:13 
[error] 3132 |        case t: (A, U) @unchecked           => t
[error]      |             ^^^^^^^^^^^^^^^^^^^^
[error]      |             Unreachable case
[error] one error found

https://github.com/apache/pekko/actions/runs/9985318652/job/27595952763?pr=1398#step:6:492

[WojciechMazur]

It seems like we unfortunately backported a change that caused a regression, it can be minimized to

def Test[U, A](thisElem: A, thatElem: U) = {
  case object passedEnd
  val any: Seq[Any] = ???
  any.zip(any)
    .map {
      case (`passedEnd`, r: U @unchecked) => (thisElem, r)
      case (l: A @unchecked, `passedEnd`) => (l, thatElem)
      case t: (A, U) @unchecked           => t
    }
}

The 3rd case is reachable so it's a bug.
I'm doing a bisect on the compiler right now before I fill in an issue in the compiler, but it seems like the regression was present in the Scala Next series since 3.4.0 (approximately introduced ~ 02.09.2023) so I'm astonished I was not reported previously.
RC2 would either revert the change that caused the regression or would include a fix