bert: properly mention deprecation of TF2 conversion script (#16171)

src/transformers/models/bert/convert_bert_original_tf2_checkpoint_to_pytorch.py

@@ -13,13 +13,16 @@
 # limitations under the License.
 
 """
-This script can be used to convert a head-less TF2.x Bert model to PyTorch, as published on the official GitHub:
-https://github.com/tensorflow/models/tree/master/official/nlp/bert
+This script can be used to convert a head-less TF2.x Bert model to PyTorch, as published on the official (now
+deprecated) GitHub: https://github.com/tensorflow/models/tree/v2.3.0/official/nlp/bert
 
 TF2.x uses different variable names from the original BERT (TF 1.4) implementation. The script re-maps the TF2.x Bert
 weight names to the original names, so the model can be imported with Huggingface/transformer.
 
 You may adapt this script to include classification/MLM/NSP/etc. heads.
+
+Note: This script is only working with an older version of the TensorFlow models repository (<= v2.3.0).
+      Models trained with never versions are not compatible with this script.
 """
 import argparse
 import os