[Speech2Text2] Skip newly added tokenizer test
The PR: https://github.com/huggingface/transformers/commit/3dd538c4d37248961d4cf99f4c07e8a5fe54984c added a new tokenizer test that should have been skipped for Speech2Text2 tokenizer. The Speech2Text2 tokenizers are yet to be added as explained in https://github.com/huggingface/transformers/pull/13186