Remove ConversationalPipeline and Conversation object (#31165)

* Remove ConversationalPipeline and Conversation object, as they have been deprecated for some time and are due for removal

* Update not-doctested.txt

* Fix JA and ZH docs

* Fix JA and ZH docs some more

* Fix JA and ZH docs some more

utils/check_docstrings.py

@@ -128,7 +128,6 @@ OBJECTS_TO_IGNORE = [
     "ConvBertTokenizerFast",
     "ConvNextConfig",
     "ConvNextV2Config",
-    "ConversationalPipeline",
     "CpmAntTokenizer",
     "CvtConfig",
     "CvtModel",

utils/not_doctested.txt

@@ -918,7 +918,6 @@ src/transformers/pipelines/audio_classification.py
 src/transformers/pipelines/audio_utils.py
 src/transformers/pipelines/automatic_speech_recognition.py
 src/transformers/pipelines/base.py
-src/transformers/pipelines/conversational.py
 src/transformers/pipelines/depth_estimation.py
 src/transformers/pipelines/document_question_answering.py
 src/transformers/pipelines/feature_extraction.py