chore: move cc to another repository (leanprover-community#34669)

`cc` tactic is replaced by `grind` and deprecated since 2025-07-31, so I created the repository [Komyyy/legacy-cc](https://github.com/Komyyy/legacy-cc) and move `cc` tactic to there.

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

Author: Komyyy

Mathlib.lean

@@ -6610,11 +6610,6 @@ public import Mathlib.Tactic.Bound.Attribute
 public import Mathlib.Tactic.Bound.Init
 public import Mathlib.Tactic.ByCases
 public import Mathlib.Tactic.ByContra
-public import Mathlib.Tactic.CC
-public import Mathlib.Tactic.CC.Addition
-public import Mathlib.Tactic.CC.Datatypes
-public import Mathlib.Tactic.CC.Lemmas
-public import Mathlib.Tactic.CC.MkProof
 public import Mathlib.Tactic.CancelDenoms
 public import Mathlib.Tactic.CancelDenoms.Core
 public import Mathlib.Tactic.Cases

Mathlib/Tactic.lean

@@ -17,11 +17,6 @@ public import Mathlib.Tactic.Bound.Attribute
 public import Mathlib.Tactic.Bound.Init
 public import Mathlib.Tactic.ByCases
 public import Mathlib.Tactic.ByContra
-public import Mathlib.Tactic.CC
-public import Mathlib.Tactic.CC.Addition
-public import Mathlib.Tactic.CC.Datatypes
-public import Mathlib.Tactic.CC.Lemmas
-public import Mathlib.Tactic.CC.MkProof
 public import Mathlib.Tactic.CancelDenoms
 public import Mathlib.Tactic.CancelDenoms.Core
 public import Mathlib.Tactic.Cases