Duplicate docs when methods=['GET', 'POST']

[mikkelee]

Hi,

When an endpoint is marked with dual methods, two docstrings are generated. Additionally, a given form parameter will show up in both GET and POST though it is only applicable for the latter.

See also: https://stackoverflow.com/questions/40744982/sphinx-autoflask-differentiate-docstrings-for-get-and-post-requests-on-same-fu