Remove the notation about 'make zookeeper'.
Remove the notation about 'make zookeeper'.

From commit 4db81cf00d4f0b6ba522244f69fa5878d15b07cc, the make
target 'zookeeper' was removed and the tox is needed to run
'make test'.

jacksontj/kazoo,python-zk/kazoo,bsanders/kazoo,python-zk/kazoo,bsanders/kazoo,AlexanderplUs/kazoo,AlexanderplUs/kazoo,jacksontj/kazoo