chore Set/UnionLift: generalize to Sort (#4071)

Co-authored-by: Komyyy <pol_tta@outlook.jp>

Mathlib/Data/Set/UnionLift.lean

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Chris Hughes
 
 ! This file was ported from Lean 3 source module data.set.Union_lift
-! leanprover-community/mathlib commit 207cfac9fcd06138865b5d04f7091e46d9320432
+! leanprover-community/mathlib commit 5a4ea8453f128345f73cc656e80a49de2a54f481
 ! Please do not edit these lines, except to modify the commit id
 ! if you have ported upstream changes.
 -/
@@ -41,7 +41,7 @@ constants, unary functions, or binary functions are preserved. These lemmas are:
 directed union, directed supremum, glue, gluing
 -/
 
-variable {α ι β : Type _}
+variable {α : Type _} {ι β : Sort _}
 
 namespace Set