Change `BloomConfig` docstring (#19336)

* change `BloomConfig` docstring

- slightly change the docstring of the `BloomConfig`
- Use correct default vocab size
- Use correct default `hidden_dim`, `n_head`

* Update src/transformers/models/bloom/configuration_bloom.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Update src/transformers/models/bloom/configuration_bloom.py
Co-authored-by: SaulLu <55560583+SaulLu@users.noreply.github.com>

* make style
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>
Co-authored-by: SaulLu <55560583+SaulLu@users.noreply.github.com>

src/transformers/models/bloom/configuration_bloom.py

@@ -53,14 +53,16 @@ class BloomConfig(PretrainedConfig):
 
 
     Args:
-        vocab_size (`int`, *optional*, defaults to 50257):
-            Vocabulary size of the Bloom model. Defines the number of different tokens that can be represented by the
-            `inputs_ids` passed when calling [`BloomModel`].
-        hidden_size (`int`, *optional*, defaults to 768):
+        vocab_size (`int`, *optional*, defaults to 250880):
+            Vocabulary size of the Bloom model. Defines the maximum number of different tokens that can be represented
+            by the `inputs_ids` passed when calling [`BloomModel`]. Check [this
+            discussion](https://huggingface.co/bigscience/bloom/discussions/120#633d28389addb8530b406c2a) on how the
+            `vocab_size` has been defined.
+        hidden_size (`int`, *optional*, defaults to 64):
             Dimensionality of the embeddings and hidden states.
-        n_layer (`int`, *optional*, defaults to 12):
+        n_layer (`int`, *optional*, defaults to 2):
             Number of hidden layers in the Transformer encoder.
-        n_head (`int`, *optional*, defaults to 12):
+        n_head (`int`, *optional*, defaults to 8):
             Number of attention heads for each attention layer in the Transformer encoder.
         layer_norm_epsilon (`float`, *optional*, defaults to 1e-5):
             The epsilon to use in the layer normalization layers.