python-markdown3.4导致 sphinx buil

https://github.com/ryanfox/sphinx-markdown-tables/issues/36

...lib/python3.7/site-packages/sphinx_markdown_tables/init.py", line 24, in process_tables
table_processor = markdown.extensions.tables.TableProcessor(md.parser)
TypeError: init() missing 1 required positional argument: 'config'

解决方法：
在requirement.txt中添加
Markdown < 3.4