configure: remove git url check

This part of the script doesn't check if git command is available and produce error if not.
It is 2 years since address changed and it is more reasonable to remove it than fix it.

Signed-off-by: Lukasz Marek <lukasz.m.luki@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
