chore: remove deprecated material from CGT (#35550)

The modules have been deprecated for 6 months. See #28063.

Author: vihdzp

Counterexamples.lean

@@ -7,7 +7,6 @@ import Counterexamples.DimensionPolynomial
 import Counterexamples.DirectSumIsInternal
 import Counterexamples.DiscreteTopologyNonDiscreteUniformity
 import Counterexamples.EulerSumOfPowers
-import Counterexamples.GameMultiplication
 import Counterexamples.Girard
 import Counterexamples.HeawoodUnitDistance
 import Counterexamples.HomogeneousPrimeNotPrime

Counterexamples/GameMultiplication.lean

@@ -6648,17 +6648,7 @@ public import Mathlib.SetTheory.Cardinal.Subfield
 public import Mathlib.SetTheory.Cardinal.ToNat
 public import Mathlib.SetTheory.Cardinal.UnivLE
 public import Mathlib.SetTheory.Descriptive.Tree
-public import Mathlib.SetTheory.Game.Basic
-public import Mathlib.SetTheory.Game.Birthday
-public import Mathlib.SetTheory.Game.Domineering
-public import Mathlib.SetTheory.Game.Impartial
-public import Mathlib.SetTheory.Game.Nim
-public import Mathlib.SetTheory.Game.Ordinal
-public import Mathlib.SetTheory.Game.Short
-public import Mathlib.SetTheory.Game.State
 public import Mathlib.SetTheory.Lists
-public import Mathlib.SetTheory.Nimber.Basic
-public import Mathlib.SetTheory.Nimber.Field
 public import Mathlib.SetTheory.Ordinal.Arithmetic
 public import Mathlib.SetTheory.Ordinal.Basic
 public import Mathlib.SetTheory.Ordinal.CantorNormalForm
@@ -6667,18 +6657,11 @@ public import Mathlib.SetTheory.Ordinal.Exponential
 public import Mathlib.SetTheory.Ordinal.Family
 public import Mathlib.SetTheory.Ordinal.FixedPoint
 public import Mathlib.SetTheory.Ordinal.FixedPointApproximants
-public import Mathlib.SetTheory.Ordinal.NaturalOps
 public import Mathlib.SetTheory.Ordinal.Notation
 public import Mathlib.SetTheory.Ordinal.Principal
 public import Mathlib.SetTheory.Ordinal.Rank
 public import Mathlib.SetTheory.Ordinal.Topology
 public import Mathlib.SetTheory.Ordinal.Veblen
-public import Mathlib.SetTheory.PGame.Algebra
-public import Mathlib.SetTheory.PGame.Basic
-public import Mathlib.SetTheory.PGame.Order
-public import Mathlib.SetTheory.Surreal.Basic
-public import Mathlib.SetTheory.Surreal.Dyadic
-public import Mathlib.SetTheory.Surreal.Multiplication
 public import Mathlib.SetTheory.ZFC.Basic
 public import Mathlib.SetTheory.ZFC.Cardinal
 public import Mathlib.SetTheory.ZFC.Class