Improve some queries in project list MRs API endpoint

What does this MR do and why?

Adding + 0 helps postgres not to use a non-efficient query plan.

Here are some before and after tests:

Projects API queries

• next page query
  • BEFORE: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/41294/commands/126953
  • AFTER: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/41294/commands/126958
• count query
  • BEFORE: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/41319/commands/127068
  • AFTER: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/41319/commands/127067

Projects GraphQL query

• BEFORE: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/41319/commands/127093
• AFTER: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/41319/commands/127094
• No noticeable difference

Disclaimer: The postgres.ai execution times (the BEFORE) seem to be way slower than production. I don't see these queries taking this long on production when I profiled the endpoints.

References

#552376 (comment 2611544544)

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Related to #552376 (closed)