R1:f92480fb7740

Fix two minor display issues with the Conduit "*.search" API documentation

Summary:
Depends on D20685. Ref T13350. Currently:

- When a SearchEngine parameter is marked as hidden from Conduit, we may still render a table of possible values. Instead, only render the table if the parameter is actually usable.
- The table header is hard-coded to say `'statuses'`, which is just a silly mistake. (Most commonly, this table does have `statuses` constants.)

Test Plan: Viewed the Conduit API documentation for…