[vulkan] Fix python overrides tests for is_vulkan_available (#39016)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/39016
Differential Revision: D21724619
Pulled By: IvanKobzarev
fbshipit-source-id: d7a6c8b944a55bc4f2cce957eeac08c5801667a0
