Fix rubocop error & warnings

[DemetrisChr]

Fix warnings:

rubocop-[...] extension supports plugin, specify `plugins: rubocop-[...]` instead of `require: rubocop-[...]` in /[...]/couchbase-ruby-client/.rubocop.yml.
For more information, see https://docs.rubocop.org/rubocop/plugin_migration_guide.html.

Warning: The `Naming/PredicateName` cop has been renamed to `Naming/PredicatePrefix`.
(obsolete configuration found in .rubocop_todo.yml, please update it)

and error:

lib/couchbase/protostellar/response_converter/search.rb:41:47: C: [Correctable] Style/RedundantParentheses: Don't use parentheses around a method call.
            r.instance_variable_set(:@fields, (proto_row.fields.to_h.transform_values { |v| JSON.parse(v) }).to_json)
                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^