Remove wsgiref from requirements.txt
Remove wsgiref from requirements.txt

wsgiref is part of python standard library since 2.5
so having it in requirements.txt has no impact.
https://docs.python.org/2/whatsnew/2.5.html#the-wsgiref-package

Change-Id: I42da2984ed4b0b0f0537274423413e1e7ff2c061

NeCTAR-RC/murano,DavidPurcell/murano_temp,sajuptpm/murano,DavidPurcell/murano_temp,chenyujie/hybrid-murano,NeCTAR-RC/murano,sajuptpm/murano,NeCTAR-RC/murano,openstack/murano,satish-avninetworks/murano,DavidPurcell/murano_temp,olivierlemasle/murano,satish-avninetworks/murano,openstack/murano,chenyujie/hybrid-murano,olivierlemasle/murano,satish-avninetworks/murano,DavidPurcell/murano_temp,olivierlemasle/murano,NeCTAR-RC/murano,olivierlemasle/murano,satish-avninetworks/murano