Cancel upcoming activities: ignore cancelled activities in queries, remove cancellable

[mna]

For #27409

Checklist for submitter

• [x] Input data is properly validated, SELECT * is avoided, SQL injection is prevented (using placeholders for values in statements)
• [ ] Added/updated automated tests
• [x] A detailed QA plan exists on the associated ticket (if it isn't there, work with the product group's QA engineer to add it)