You could delete the Mutex file from the storage/framework folder:
storage/framework/schedule-hashedname
The hard part is identifying which file to delete, since the "hashedname" part is a sha1() of the string that results from concatenating the crontab expression and command name:
sha1($this->expression.$this->command)
Source: https://github.com/laravel/framework/blob/7.x/src/Illuminate/Console/Scheduling/Event.php#L207