shells/fish: fix completions for python

Eliminate errors during command completion for python, python2, and python3 if
the /usr/local/bin/python symlink does not exist. Additionally, even if the
symlink does exist, the completions will be wrong for the non-default
interpreter. So I'm simply deleting the problematic completions altogether. I
opened an upstream bug for the latter issue.

https://github.com/fish-shell/fish-shell/issues/3840

While I'm here, delete an extraneous patch file for DOCS=off

PR: 216987
Reported by: Keren Sky <keren_sky@live.com>
Approved by: brd (ports, implicit)