Fix get_objects fails with attributesToRetrieve

[camel2243]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Related Issue	Fix #469
Need Doc update	no

Describe your change

Fix the incorrect opts passed to get_objects

What problem is this fixing?

When passing opts: attributesToRetrieve to get_objects we receive an excpetion that attributesToRetrieve is an invalid key. attributesToRetrieve is supported in request_options, not in opts.

Here is the proof:

[1] pry(#<Algolia::Search::Index>)> opts
=> {:attributesToRetrieve=>"id"}

[2] pry(#<Algolia::Search::Index>)> @transporter.read(:POST, '/1/indexes/*/objects', { 'requests': requests }, opts)
Algolia::AlgoliaHttpError: invalid key 'attributesToRetrieve'. Expected: appID, apiKey, requests, allowNestedFacets (near 1:112)
from /Users/camel/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/algolia-2.3.4/lib/algolia/transport/transport.rb:74:in `block in request'

[3] pry(#<Algolia::Search::Index>)> @transporter.read(:POST, '/1/indexes/*/objects', { 'requests': requests }, {})
=> {:results=>[{:id=>1, :objectID=>"1"}]}