Avoid many failing tests in doctesting
Author: ydshieh
Pull request: yes

# What does this PR do?

Avoid many failing tests in doctesting: currently, src/transformers/models/blip_2/modeling_blip_2.py and docs/source/en/tasks/idefics.md cause problem to other tests

With this PR: the failing list is much shorter
```
transformers.generation.configuration_utils.GenerationConfig.from_pretrained
transformers.generation.logits_process.ExponentialDecayLengthPenalty
transformers.generation.logits_process.WhisperTimeStampLogitsProcessor
transformers.models.wav2vec2.tokenization_wav2vec2.Wav2Vec2CTCTokenizer.decode
transformers.models.wav2vec2_with_lm.processing_wav2vec2_with_lm.Wav2Vec2ProcessorWithLM.decode
transformers.models.whisper.modeling_whisper.WhisperForCausalLM.forward
```

Currently failing tests without this PR

```
transformers.generation.configuration_utils.GenerationConfig.from_pretrained
transformers.generation.logits_process.ExponentialDecayLengthPenalty
transformers.generation.logits_process.WhisperTimeStampLogitsProcessor
transformers.models.mbart.modeling_tf_mbart.TFMBartForConditionalGeneration.call
transformers.models.mbart.modeling_tf_mbart.TFMBartModel.call
transformers.models.mobilevit.modeling_tf_mobilevit.TFMobileViTForSemanticSegmentation.call
transformers.models.opt.modeling_tf_opt.TFOPTForCausalLM.call
transformers.models.opt.modeling_tf_opt.TFOPTModel.call
transformers.models.regnet.modeling_tf_regnet.TFRegNetForImageClassification.call
transformers.models.regnet.modeling_tf_regnet.TFRegNetModel.call
transformers.models.resnet.modeling_tf_resnet.TFResNetForImageClassification.call
transformers.models.resnet.modeling_tf_resnet.TFResNetModel.call
transformers.models.roberta.modeling_tf_roberta.TFRobertaForCausalLM.call
transformers.models.roberta.modeling_tf_roberta.TFRobertaForMaskedLM.call
transformers.models.roberta.modeling_tf_roberta.TFRobertaForMultipleChoice.call
transformers.models.roberta.modeling_tf_roberta.TFRobertaForQuestionAnswering.call
transformers.models.roberta.modeling_tf_roberta.TFRobertaForSequenceClassification.call
transformers.models.roberta.modeling_tf_roberta.TFRobertaForTokenClassification.call
transformers.models.roberta.modeling_tf_roberta.TFRobertaModel.call
transformers.models.roberta_prelayernorm.modeling_tf_roberta_prelayernorm.TFRobertaPreLayerNormForCausalLM.call
transformers.models.roberta_prelayernorm.modeling_tf_roberta_prelayernorm.TFRobertaPreLayerNormForMaskedLM.call
transformers.models.roberta_prelayernorm.modeling_tf_roberta_prelayernorm.TFRobertaPreLayerNormForMultipleChoice.call
transformers.models.roberta_prelayernorm.modeling_tf_roberta_prelayernorm.TFRobertaPreLayerNormForQuestionAnswering.call
transformers.models.roberta_prelayernorm.modeling_tf_roberta_prelayernorm.TFRobertaPreLayerNormForSequenceClassification.call
transformers.models.roberta_prelayernorm.modeling_tf_roberta_prelayernorm.TFRobertaPreLayerNormForTokenClassification.call
transformers.models.roberta_prelayernorm.modeling_tf_roberta_prelayernorm.TFRobertaPreLayerNormModel.call
transformers.models.segformer.modeling_tf_segformer.TFSegformerForImageClassification.call
transformers.models.segformer.modeling_tf_segformer.TFSegformerForSemanticSegmentation.call
transformers.models.segformer.modeling_tf_segformer.TFSegformerModel.call
transformers.models.vision_text_dual_encoder.modeling_tf_vision_text_dual_encoder.TFVisionTextDualEncoderModel.call
transformers.models.vision_text_dual_encoder.modeling_tf_vision_text_dual_encoder.TFVisionTextDualEncoderModel.from_vision_text_pretrained
```

Comments:
_The documentation is not available anymore as the PR was closed or merged._