Fix Albert Attention
This PR simplifies  the code of class AlbertAttention.
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/4188?src=pr&el=h1) Report
> Merging [#4188](https://codecov.io/gh/huggingface/transformers/pull/4188?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/877fc56410e3a0495f62e07e66a73e6b3b9629bc&el=desc) will **increase** coverage by `0.00%`.
> The diff coverage is `100.00%`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/4188/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/4188?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master    #4188   +/-   ##
=======================================
  Coverage   78.10%   78.11%           
=======================================
  Files         117      117           
  Lines       18962    18963    +1     
=======================================
+ Hits        14811    14813    +2     
+ Misses       4151     4150    -1     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/4188?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/modeling\_albert.py](https://codecov.io/gh/huggingface/transformers/pull/4188/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ19hbGJlcnQucHk=) | `75.38% <100.00%> (+0.06%)` | :arrow_up: |
| [src/transformers/modeling\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/4188/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ191dGlscy5weQ==) | `90.92% <0.00%> (-0.13%)` | :arrow_down: |
| [src/transformers/modeling\_tf\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/4188/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl91dGlscy5weQ==) | `92.93% <0.00%> (+0.32%)` | :arrow_up: |

------

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> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/4188?src=pr&el=footer). Last update [877fc56...7c64f23](https://codecov.io/gh/huggingface/transformers/pull/4188?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
<|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
