Update bleach to 6.0.0

[pyup-bot]

This PR updates bleach from 4.1.0 to 6.0.0.

Changelog

5.0.1

-------------------------------

**Bugs**

* Add missing comma to tinycss2 require. Thank you, shadchin!

* Add url parse tests based on wpt url tests. (688)

* Support scheme-less urls if "https" is in allow list. (662)

* Handle escaping ``<`` in edge cases where it doesn't start a tag. (544)

* Fix reference warnings in docs. (660)

* Correctly urlencode email address parts. Thank you, larseggert! (659)

5.0.0

-------------------------------

**Backwards incompatible changes**

* ``clean`` and ``linkify`` now preserve the order of HTML attributes. Thank
you, askoretskly! (566)

* Drop support for Python 3.6. Thank you, hugovk! (629)

* CSS sanitization in style tags is completely different now. If you're using
Bleach ``clean`` to sanitize css in style tags, you'll need to update your
code and you'll need to install the ``css`` extras::

   pip install 'bleach[css]'

See `the documentation on sanitizing CSS for how to do it
<https://bleach.readthedocs.io/en/latest/clean.html#sanitizing-css>`_. (633)

**Bug fixes**

* Rework dev dependencies. We no longer have
``requirements-dev.in``/``requirements-dev.txt``. Instead, we're using
``dev`` extras.

See `development docs <https://bleach.readthedocs.io/en/latest/dev.html>`_
for more details. (620)

* Add newline when dropping block-level tags. Thank you, jvanasco! (369)

Links

• PyPI: https://pypi.org/project/bleach
• Changelog: https://pyup.io/changelogs/bleach/
• Repo: https://github.com/mozilla/bleach
• Docs: https://pythonhosted.org/bleach/