Regression in `mjakubowski84/parquet4s` for type inference about dotty

[KacperFKorban]

A slightly smaller minimization:

//> using scala 3.nightly

class Box[+O]:
  def ++[O2 >: O](other: Box[O2]): Box[O2] = ???
object Box:
  val empty: Box[Nothing] = ???

def test[T]: Box[T] =
  List(Box.empty, Box.empty)
    // .reduceOption[Box[T]](_ ++ _) // works
    .reduceOption(_ ++ _) // fails
    .getOrElse(Box.empty)

Output:

-- [E007] Type Mismatch Error: ~/bugs/i21275.scala:13:14 ---------------
10 |  List(Box.empty, Box.empty)
11 |    // .reduceOption[Box[T]](_ ++ _) // works
12 |    .reduceOption(_ ++ _) // fails
13 |    .getOrElse(Box.empty)
   |  ^
   |  Found:    Box[Any]
   |  Required: Box[T]
   |
   | longer explanation available when compiling with `-explain`

[Gedochao]

cc @odersky @dwijnand