Fix group authorization when searching for epics

What does this MR do and why?

Follow up of !93601 (merged).

On the MR above I forgot to take into account projects that are visible to the user to get authorized groups, in other words, if a group has a project all group members can read ancestor groups.

More details at #371067 (closed)

This changes one of the queries of the union introduced by !93601 (merged), it gets a bit worse performance-wise, but we need to keep the same behavior from before at least until we remove this authorization inconsistency.

• Query diff: https://www.diffchecker.com/GDYpyfUt
• Old query and plans: https://console.postgres.ai/gitlab/gitlab-production-tunnel-pg12/sessions/11603/commands/41232
• New query and plans: https://console.postgres.ai/gitlab/gitlab-production-tunnel-pg12/sessions/11603/commands/41234

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