Remove TypeSystem.isOverrideSubtypeOf()
Remove TypeSystem.isOverrideSubtypeOf()

It is replaced with CorrectOverrideHelper.

Change-Id: Iab8162b9ffbca02000587ece1215717346b0a3a7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/134203
Reviewed-by: Paul Berry <72d414e3a99fb120308437779d51667bcc0984eb@google.com>
Commit-Queue: Konstantin Shcheglov <09e4d7516628963212bf4aace2f97603d2b706e4@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk