Disable pytest messing with warnings.

We may be able to remove this if pytest resolves pytest-dev/pytest#2430, but until that point we need to turn the old behaviour back on.

I want to point out that it's pretty stupid that we have to do this, but there we are.

# [Codecov](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=h1) Report
> Merging [#4056](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=desc) into [master](https://codecov.io/gh/kennethreitz/requests/commit/dbb67a13109edef8d02addf5b3fbc8c6f319f4aa?src=pr&el=desc) will **increase** coverage by `3.08%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/kennethreitz/requests/pull/4056/graphs/tree.svg?height=150&token=mZGswIiXLa&width=650&src=pr)](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #4056      +/-   ##
==========================================
+ Coverage   86.66%   89.75%   +3.08%     
==========================================
  Files          15       15              
  Lines        1942     1942              
==========================================
+ Hits         1683     1743      +60     
+ Misses        259      199      -60
```


| [Impacted Files](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [requests/adapters.py](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=tree#diff-cmVxdWVzdHMvYWRhcHRlcnMucHk=) | `92.92% <0%> (+0.47%)` | :arrow_up: |
| [requests/sessions.py](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=tree#diff-cmVxdWVzdHMvc2Vzc2lvbnMucHk=) | `93.95% <0%> (+1.42%)` | :arrow_up: |
| [requests/models.py](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=tree#diff-cmVxdWVzdHMvbW9kZWxzLnB5) | `93.42% <0%> (+2.26%)` | :arrow_up: |
| [requests/\_internal\_utils.py](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=tree#diff-cmVxdWVzdHMvX2ludGVybmFsX3V0aWxzLnB5) | `100% <0%> (+6.25%)` | :arrow_up: |
| [requests/utils.py](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=tree#diff-cmVxdWVzdHMvdXRpbHMucHk=) | `86.25% <0%> (+7%)` | :arrow_up: |
| [...es/urllib3/packages/ssl\_match\_hostname/\_\_init\_\_.py](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=tree#diff-cmVxdWVzdHMvcGFja2FnZXMvdXJsbGliMy9wYWNrYWdlcy9zc2xfbWF0Y2hfaG9zdG5hbWUvX19pbml0X18ucHk=) | `93.54% <0%> (+9.67%)` | :arrow_up: |
| [requests/packages/chardet/compat.py](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=tree#diff-cmVxdWVzdHMvcGFja2FnZXMvY2hhcmRldC9jb21wYXQucHk=) | `100% <0%> (+35.13%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=footer). Last update [dbb67a1...f3d310b](https://codecov.io/gh/kennethreitz/requests/pull/4056?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).


> I want to point out that it's pretty stupid that we have to do this, but there we are.

Hi @Lukasa, sorry to hear that this affected you guys so. We are having some discussion related to this on pytest-dev/pytest#2430, it mean a lot if you could join the discussion and share your thoughts. 👍 

@niccoddemus Yeah, I saw that thread. I am not sure how much value I can provide by weighing in: your warnings filter as added prevented us from tweaking the filter ourselves for testing purposes. I can drop in though.