s2s: fix LR logging, remove some dead code.
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/6205?src=pr&el=h1) Report
> Merging [#6205](https://codecov.io/gh/huggingface/transformers/pull/6205?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/82a0e2b67ec94d28b20e24b3393644002bbd0d4b&el=desc) will **increase** coverage by `0.07%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/6205/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/6205?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #6205      +/-   ##
==========================================
+ Coverage   79.65%   79.73%   +0.07%     
==========================================
  Files         146      146              
  Lines       26607    26607              
==========================================
+ Hits        21194    21214      +20     
+ Misses       5413     5393      -20     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/6205?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/tokenization\_xlm\_roberta.py](https://codecov.io/gh/huggingface/transformers/pull/6205/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90b2tlbml6YXRpb25feGxtX3JvYmVydGEucHk=) | `84.52% <0.00%> (-10.72%)` | :arrow_down: |
| [src/transformers/generation\_tf\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/6205/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9nZW5lcmF0aW9uX3RmX3V0aWxzLnB5) | `81.70% <0.00%> (+1.00%)` | :arrow_up: |
| [src/transformers/tokenization\_bart.py](https://codecov.io/gh/huggingface/transformers/pull/6205/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90b2tlbml6YXRpb25fYmFydC5weQ==) | `95.77% <0.00%> (+35.21%)` | :arrow_up: |

------

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> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/6205?src=pr&el=footer). Last update [82a0e2b...f39a67f](https://codecov.io/gh/huggingface/transformers/pull/6205?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
