fix(Combinatorics/Enumerative/Bonferroni): make "Bonferroni.lean" a module

Author: Deep0Thinking

Mathlib/Combinatorics/Enumerative/Bonferroni.lean

@@ -3,7 +3,9 @@ Copyright (c) 2026 Louis (Yiyang) Liu. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Louis (Yiyang) Liu
 -/
-import Mathlib.Data.Nat.Choose.Sum
+module
+
+public import Mathlib.Data.Nat.Choose.Sum
 
 /-!
 # Bonferroni inequalities
@@ -23,6 +25,8 @@ by truncating the inclusion–exclusion formula for a finite union of sets.
   the cardinality of the union.
 -/
 
+@[expose] public section
+
 open Nat Int Set
 
 /-! ### Binomial identities -/