package/python-*: drop redundant python || python3 dependencies

As discussed on the list:

http://lists.busybox.net/pipermail/buildroot/2014-November/112509.html



We currently have a mix of python packages explicitly depending on python ||
python3 in their Config.in and packages that don't.  As all python packages
are inside a python || python3 conditional in the main Config.in, the
explicit dependencies inside the package Config.in is redundant, so drop it
for consistency.

Automated using:

sed -i '/depends on BR2_PACKAGE_PYTHON.*PYTHON3/d' package/python-*/Config.in

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>