Remove update_service_capabilities from scheduler rpc api

This method was already unused in the code base, so it can be
immediately removed from the client rpc api.  It must remain on the
server side (scheduler manager) until the api receives a major version
bump.

Related to blueprint rpc-major-version-updates-icehouse

Change-Id: I689bef71cc3db887bc571b9c364ee906a5a927f4
Merge "Remove update_service_capabilities from scheduler rpc api"