Fix migration failure for missing procrastinate_jobs_queue_name_idx

[medihack]

Closes #1461

The index procrastinate_jobs_queue_name_idx was added to schema.sql in v0.11.0 but lacked a corresponding migration. The migration 03.00.00_50_post_cancel_notification.sql tried to rename this index, which failed for users who only used migrations to set up their database.

This fix adds the missing historical migration file at the correct version (00.11.00_04_add_jobs_queue_name_idx.sql) to create the index. This allows the later migration to simply rename it as originally intended.

Successful PR Checklist:

• [ ] Tests
  • [x] (not applicable?)
• [ ] Documentation
  • [x] (not applicable?)

PR label(s):

• [ ] https://github.com/procrastinate-org/procrastinate/labels/PR%20type%3A%20breaking%20%F0%9F%92%A5
• [ ] https://github.com/procrastinate-org/procrastinate/labels/PR%20type%3A%20feature%20%E2%AD%90%EF%B8%8F
• [x] https://github.com/procrastinate-org/procrastinate/labels/PR%20type%3A%20bugfix%20%F0%9F%95%B5%EF%B8%8F
• [ ] https://github.com/procrastinate-org/procrastinate/labels/PR%20type%3A%20miscellaneous%20%F0%9F%91%BE
• [ ] https://github.com/procrastinate-org/procrastinate/labels/PR%20type%3A%20dependencies%20%F0%9F%A4%96
• [ ] https://github.com/procrastinate-org/procrastinate/labels/PR%20type%3A%20documentation%20%F0%9F%93%9A

[medihack]

I am not sure if it is as easy as this, or whether we should ignore the failing test (which is done for new migrations, not for retrospectively added ones).