chore: test cancel_match

[lyon-1050]

1. cancel_match — redundant state check (applied)

The original checked state == Active then separately state != Pending. The second check already covers Active and every other non-Pending state. Collapsed into a
single check that maps the state to the correct error.

2. add_allowed_token — duplicated append_allowed_token call (applied)

The if !already_allowed / else block called Self::append_allowed_token at the end of both branches — identical code. Lifted it out of the conditional so it runs
once unconditionally after the branching logic.

3. create_match — missing self-contract check for player1 (interrupted)

The original only checked that player2 != contract_address. player1 had the same potential problem but was never validated against it. The fix extends the guard
to cover both players in a single condition.

closes #795