[Bug]: Fix typo in slash-command tournaments documentation

[voyager-slama]

Describe the bug

The slash-command tournaments description contains a typo.

How can we recreate this bug?

1. Follow the affected workflow described above.
2. Observe the behavior.

Expected behavior

Correct documentation wording so the command reference is accurate.

MatchExec Version

Unknown — migrated from Todoist; determine during triage.

Docker Version

Unknown — migrated from Todoist; determine during triage.

Additional context

Correct documentation wording so the command reference is accurate.

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Migrated from Todoist by voyager[bot].