mgr/cephadm: remove Dir_Chunk = 0

This breaks RGW exports, and is likely to be beneficial for libcephfs.

Signed-off-by: Sage Weil <sage@newdream.net>

src/pybind/mgr/cephadm/templates/services/nfs/ganesha.conf.j2

@@ -9,10 +9,6 @@ NFS_CORE_PARAM {
 {% endif %}
 }
 
-MDCACHE {
-        Dir_Chunk = 0;
-}
-
 EXPORT_DEFAULTS {
         Attr_Expiration_Time = 0;
 }