pip_requirements: ease the dependency on specific version of modules.
pip_requirements: ease the dependency on specific version of modules.

Since it's not necessary to explicitly tie XinUI with modules such as
ryu==3.6, etc., I think it's okat to let users meet requirements if
they have newer modules installed.

Signed-off-by: Wei-Li Tang <5d755dd15206b0463ba6e773187c465627300b40@xinguard.com>

xinguard/XinUI,xinguard/XinUI