Remove nova.cache_utils oslo.config.opts entrypoint

There was never a list_opts method in nova.cache_utils,
and the options registeration was moved to nova.conf.cache
in 466bce576a so we can
cleanup the entrypoint.

Change-Id: If02620752c1bb018117f2c6755d9b9661185e4d6

setup.cfg

@@ -30,7 +30,6 @@ oslo.config.opts =
     nova.conf = nova.conf.opts:list_opts
     nova.compute = nova.compute.opts:list_opts
     nova.virt = nova.virt.opts:list_opts
-    nova.cache_utils = nova.cache_utils:list_opts
 
 oslo.config.opts.defaults =
     nova.api = nova.common.config:set_middleware_defaults