Add missing test dependency on dev-ruby/rspec:2. Required because we
need to ensure that we don't load rspec 3 when it is present and we
cannot do that without using the gem versioning.
Fixes: https://bugs.gentoo.org/635092
Package-Manager: Portage-2.3.66, Repoman-2.3.16 Signed-off-by: Hans de Graaff <graaff@gentoo.org>