fix: wrong architecture count in README
Just say “the following” so that this intro doesn't so easily fall out of date :)
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/2203?src=pr&el=h1) Report
> Merging [#2203](https://codecov.io/gh/huggingface/transformers/pull/2203?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/94c99db34cf9074a212c36554fb925c513d70ab1?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/2203/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/transformers/pull/2203?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master    #2203   +/-   ##
=======================================
  Coverage   81.47%   81.47%           
=======================================
  Files         122      122           
  Lines       18342    18342           
=======================================
  Hits        14945    14945           
  Misses       3397     3397
```



------

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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/2203?src=pr&el=footer). Last update [94c99db...a297846](https://codecov.io/gh/huggingface/transformers/pull/2203?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
<|||||>This is a good idea :) @thomwolf 