pyp2rpm converts all extras to runtime Requires

I've noticed here and here:

https://bugzilla.redhat.com/show_bug.cgi?id=2083243 fastbencode 0.0.7
https://bugzilla.redhat.com/show_bug.cgi?id=2058961 unicodedata2 14.0.0

In both cases, the extras used to build/test the package were converted to runtime requires.

[`fastbencode[cext]`](https://github.com/breezy-team/fastbencode/blob/v0.0.7/setup.py#L134) caused:

```
Requires: python3dist(cython) >= 0.29
```

[`unicodedata2[testing]`](https://github.com/fonttools/unicodedata2/blob/14.0.0/setup.py#L42) caused:

```
Requires: python3dist(coverage)
Requires: python3dist(pytest)
Requires: python3dist(pytest-randomly)
Requires: python3dist(pytest-xdist)
```

This is not a good idea. Those are build dependencies, not runtime dependencies. pyp2rpm cannot know if the extras are useful at runtime or not.