Remove unused `dump` method from VSX vec256 methods (#66085)
Summary:
Follow up after https://github.com/pytorch/pytorch/pull/63533
Probably fixes https://github.com/pytorch/pytorch/issues/65956
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66085
Reviewed By: ngimel
Differential Revision: D31382898
Pulled By: malfet
fbshipit-source-id: f3d97b0f2c7f1207827773ae85e2739f1d54b9c7
