Fix DeBERTa integration tests
Fix the two DeBERTa integration tests.

- The classification test doesn't actually make sense, since there is no classification head saved in `microsoft/deberta-base`
- Fix to the way the attention was initialized according to the pos type.

closes https://github.com/huggingface/transformers/issues/7565
closes https://github.com/huggingface/transformers/pull/7645