Fix/don't reschedule suspended cards

[L-M-Sherlock]

[iamllama]

For context, this fixes an attempt to subtract with overflow panic at https://github.com/ankitects/anki/blob/5614d20bedcc4dd268136d389ad796b404a69d2c/rslib/src/scheduler/fsrs/rescheduler.rs?plain=1#L89 when run via ./run (went unnoticed in release as rust doesn't panic during overflows then)

[L-M-Sherlock]

In addition to @iamllama's context:

https://github.com/ankitects/anki/blob/2d4de33cf3160342c4c704c294e643c3e11071b1/rslib/src/storage/card/deck_due_counts.sql#L1-L14

The count doesn't include suspended cards.