Remove simplejson useless requirement
Remove simplejson useless requirement

This patch cleans up the requirement list to remove simplejson module
that is not used anymore directly by monasca-agent.

Change-Id: I7f7aea7cb28ef428f1559e59e2c6f0fa25a7e65c

sapcc/monasca-agent,sapcc/monasca-agent,sapcc/monasca-agent