Advanced Search should index trials on GitLab.com regardless of seat count

Problem

Internal slack thread: https://gitlab.slack.com/archives/C3TMLK465/p1626093978320700

We have seen a reoccurring situation on GitLab.com where subscription trials are not getting the seats attribute set to > 0. The check for indexing a namespace into Elasticsearch in gitlab_subscription.rb looks at seats count and whether the plan is a paid and hosted plan.

Proposal

Add an additional check in the automatically_index_in_elasticsearch? method to index all trials regardless of seat count. I would not recommend changing the has_a_paid_hosted_plan? method as it is used in other areas unrelated to Advanced Search.