(hotfix) Write about annotations of common methods

In https://github.com/jubatus/website/issues/87, I said like followings:

> common RPC methods (save, load ..) are not defined in IDL. So, user can not know Lock-type easily (Other than to read source code *_impl.cpp).

> How about adding Lock-type in Client API page?

But, I reconsidered that there is no need to document about Lock-type of each common methods.

Then instead, I described that "Annotations of common methods are specified by jenerator" in server.html