Fixed typo in README.rst
Fixed typo in README.rst

"Sphinix" -> "Sphinx"

Change-Id: I2a3b9e508d8070a429aecb0e4f91160d68844950
Signed-off-by: Jan Hilberath <14e793d896ddc8ca6911747228e86464cf420065@midokura.com>

celebdor/kuryr-libnetwork,celebdor/kuryr,midonet/kuryr,midonet/kuryr,openstack/kuryr,celebdor/kuryr,midonet/kuryr,celebdor/kuryr-libnetwork,celebdor/kuryr-libnetwork,openstack/kuryr