chore(category_theory/concrete_category): remove imports (#17093)

Remove unneeded imports. This had resulted in someone incorrectly thinking that it was block for porting to mathlib4, so may as well clean up.



Co-authored-by: Scott Morrison <scott.morrison@gmail.com>

src/category_theory/concrete_category/bundled.lean

@@ -3,7 +3,7 @@ Copyright (c) 2018 Scott Morrison. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Scott Morrison, Johannes Hölzl, Reid Barton, Sean Leather
 -/
-import tactic.pi_instances
+import tactic.lint
 
 /-!
 # Bundled types