[Dbix-class] Tiny documentation patch

[Peter Rabbitson]

Peter Valdemar Mørch wrote:
> Bascially 4*
> 
> -more info see L<DBIx::Class::Relationship/condition>.
> +more info see L<DBIx::Class::Relationship::Base/condition>.
> 

This finally got applied: https://github.com/dbsrgits/dbix-class/commit/6c30f9c308d6c2f2d6ad82bce84dc70cbd408852#diff-1

Thank you!