Bug - Non-default variant shows up as default

If the first variant in the variants list is not set to default: false then it is considered default. This code https://gitlab.com/meltano/hub/-/blob/main/_plugins/plugin_enricher.rb#L39. It shouldnt care about order.

In !213 (merged) the second in the list was set to default and the default key removed from the original which is still first in the list. I think the first should be default unless others have default: true.