Provide valid object types in _find API doc

[jsevidal13]

Summary

The current Find objects API documentation requires the object type as a query parameter:

To further clarify these requirements, it is requested to include within this description the valid options available, similar to the way it is included in the Get object API documentation:

Checklist

Delete any items that are not applicable to this PR.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
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For maintainers

• This was checked for breaking API changes and was labeled appropriately

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