Improve performance of snippets_controller spec

What does this MR do?

In this MR we improve the performance of the spec spec/controllers/snippets_controller_spec.rb. In local the spec takes 1 minute and 29 seconds and 1087 queries. After the improvement, it takes 1 minute and 4 seconds and 836 queries.

Does this MR meet the acceptance criteria?

Conformity

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

Related to #228709 (closed)