textproc/py-sphinxcontrib-serializinghtml: Update to 2.0.0

• Update WWW
• Update LICENSE_FILE
• Convert to USE_PYTHON=pep517

Changes: https://github.com/sphinx-doc/sphinxcontrib-serializinghtml/releases

		https://github.com/sphinx-doc/sphinxcontrib-serializinghtml/blob/master/CHANGES.rst