Replace .having with .where in calendar query

What does this MR do?

the current syntax doesn't work properly in Rails 5, the resulting query looks like:

HAVING "events"."project_id" IN (0)

instead of:

HAVING "events"."project_id" IN (SELECT "projects"."id" FROM...

Also we should not use ActiveRecord internal methods. In this case we can filter projects in WHERE clause instead of doing this in HAVING clause. Usage of WHERE should be also more efficient because grouping is then done on much smaller subset of records.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #46964 (closed)