Update convbert doc

Author: jplu

src/transformers/models/convbert/modeling_tf_convbert.py

@@ -803,12 +803,15 @@ class TFConvBertPreTrainedModel(TFPreTrainedModel):
             vectors than the model's internal embedding lookup matrix.
         output_attentions (:obj:`bool`, `optional`):
             Whether or not to return the attentions tensors of all attention layers. See ``attentions`` under returned
-            tensors for more detail.
+            tensors for more detail. This argument can be used only in eager mode, in graph mode the value in the
+            config will be used instead.
         output_hidden_states (:obj:`bool`, `optional`):
             Whether or not to return the hidden states of all layers. See ``hidden_states`` under returned tensors for
-            more detail.
+            more detail. This argument can be used only in eager mode, in graph mode the value in the config will be
+            used instead.
         return_dict (:obj:`bool`, `optional`):
-            Whether or not to return a :class:`~transformers.file_utils.ModelOutput` instead of a plain tuple.
+            Whether or not to return a :class:`~transformers.file_utils.ModelOutput` instead of a plain tuple. This
+            argument can be used in eager mode, in graph mode the value will always be set to True.
         training (:obj:`bool`, `optional`, defaults to :obj:`False`):
             Whether or not to use the model in training mode (some modules like dropout modules have different
             behaviors between training and evaluation).