doc: Use wildcard instead of explicit file list
doc: Use wildcard instead of explicit file list

As per request here:
https://github.com/memcached/memcached/pull/554#issuecomment-543362675

NB: Using wildcards for dependencies with Automake is not recommended
and should be considered fragile. However, for this particular case it
seems to work.

memcached/memcached,dormando/memcached,memcached/memcached,dormando/memcached,dormando/memcached,memcached/memcached,memcached/memcached,memcached/memcached,dormando/memcached,dormando/memcached