www_coderepo: do not copy {-code_repos} from config

www_coderepo: do not copy {-code_repos} from config

Avoiding 2 extra hash lookups per-request when we do plenty more
isn't worth the static memory overhead.  This shaves another chunk
off our memory use:

$ perl -MDevel::Size=total_size -I lib -MPublicInbox::WwwCoderepo -E \
  'say total_size(PublicInbox::WwwCoderepo->new(PublicInbox::Config->new))'

before: 1184385
 after: 1020878