Fix T5 v1.1 detection (#43681)
* Fix T5 v1.1 detection
PR #41541 refactored `tie_word_embeddings` handling (among other things)
which subtly broke detection of T5 v1.1 vs. original detection. As a
consequence, decoder output scaling was always applied, regardless of
T5 version.
This is resolved by using the correct value for `tie_word_embeddings`.
**Testing:**
This was not covered by the tests since the tests instantiate the config
once and modify attributes on the config. This is problematic since all
the decision logic is happening in `T5Config.__init__`. This was addressed
by having a specific `get_config_v1_1` method that initializes the
config as if it were coming from a v1.1 model (e.g., flan-t5).
* Make repo consistent
* Make repo consistent
* mt5 isn't copied from t5 anymore
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Co-authored-by: nemo <git@ningu.net>
Co-authored-by: raushan <raushan@huggingface.co>
