Improve spec performance for snippets API specs

What does this MR do?

This MR is a first attempt to improve the performance of spec/requests/api/snippets_spec.rb

When run locally, the time reduces from 50.11s to 46.16s, a minor improvement of 3.95s

DB queries reduced from 3864 to 3219. Factory usage reduced from 224 to 162.

Queries saved: 645

Contributes to https://gitlab.com/gitlab-org/plan/-/issues/145

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content