Type update_seq as optional in DocumentViewResponse

[vividn]

Overview

When calling db.view, a value for update_seq is only returned if requested in the params with update_seq: true. Therefore, the type for the response in DocumentViewResponse should have this as optional

Testing recommendations

Call any view with update_seq: false in the params, notice how update_seq is not in the return value

Checklist

• [x] Code is written and works correctly;
• (N/A) Changes are covered by tests;
• (N/A) Documentation reflects the changes;