[aur-general] Rename/Remove of aur sympy git package

[Yichao Yu]

The old python-sympy-git package is actually a python2 package, I have
just adopted it and uploaded a python2-sympy-git to replace the old
one.

Please remove python3-sympy-git (which is my package uploaded before I
adopted python-...) and possibly swap the vote of python-sympy-git and
python2-sympy-git (also swap contributor if possible ~~~~)

THX

links to relative packages:
https://aur.archlinux.org/packages.php?ID=56954
https://aur.archlinux.org/packages.php?ID=23341
https://aur.archlinux.org/packages.php?ID=56921