Update malware scan configuration

Edits one Malware Scanner global configuration. Send only what changes; answers **200** with the configuration document. **Body** (JSON), every field optional except that `tier` is never accepted here (**422** - a configuration's tier cannot change after creation; create a new one instead): `name`, `schedule`, `extensions`, `max_file_size`, `default` - the same fields and values as "Create malware scan configuration". - `schedule` is replaced whole: when it is sent it carries every field its frequency needs; when it is left out the stored one stays. Sending a `schedule.frequency` other than `monthly` on a basic configuration answers 422. - A new schedule reaches every website that uses the configuration and reschedules their next scan. - `default: true` makes it the configuration new websites receive and takes the mark off the previous one; `default: false` clears it. `region` and `batch` are never accepted here and answer 422. Editing a **premium** configuration answers **403** for an organization without the addon, whatever the current tier - the current state is what gates, the same as "Create malware scan configuration" and "Assign websites to a malware scan configuration". Requires a full-access token (read-only tokens answer 403). A configuration of another organization answers 404.