Generate: post-generate config doctest fix (#20804)

* fix doctests

* revert unwanted change

src/transformers/generation/utils.py

@@ -2024,7 +2024,7 @@ class GenerationMixin:
         >>> model = AutoModelForCausalLM.from_pretrained("gpt2")
 
         >>> # set pad_token_id to eos_token_id because GPT2 does not have a PAD token
-        >>> model.config.pad_token_id = model.config.eos_token_id
+        >>> model.generation_config.pad_token_id = model.generation_config.eos_token_id
 
         >>> input_prompt = "It might be possible to"
         >>> input_ids = tokenizer(input_prompt, return_tensors="pt").input_ids
@@ -2032,7 +2032,7 @@ class GenerationMixin:
         >>> # instantiate logits processors
         >>> logits_processor = LogitsProcessorList(
         ...     [
-        ...         MinLengthLogitsProcessor(10, eos_token_id=model.config.eos_token_id),
+        ...         MinLengthLogitsProcessor(10, eos_token_id=model.generation_config.eos_token_id),
         ...     ]
         ... )
         >>> stopping_criteria = StoppingCriteriaList([MaxLengthCriteria(max_length=20)])
@@ -2272,7 +2272,7 @@ class GenerationMixin:
         >>> # instantiate logits processors
         >>> logits_processor = LogitsProcessorList(
         ...     [
-        ...         MinLengthLogitsProcessor(15, eos_token_id=model.config.eos_token_id),
+        ...         MinLengthLogitsProcessor(15, eos_token_id=model.generation_config.eos_token_id),
         ...     ]
         ... )
         >>> # instantiate logits processors