[DOC] Update host refine default

[shainotshy1]

Report incorrect documentation

Location of incorrect documentation
(

cuvs/cpp/src/neighbors/refine/refine_host.hpp

Line 179 in 9dc3a4d

cuvs::distance::DistanceType metric = cuvs::distance::DistanceType::L2Unexpanded)

)

Describe the problems or issues found in the documentation
The default value for the metric is for host refine is L2Unexpanded however the only supported metrics are L2Expanded and InnerProduct.

Steps taken to verify documentation is incorrect
Ran refinement without passing in value for metric and this fails to run to due to "Unsupported metric."

Suggested fix for documentation
Change default to L2Expanded or support L2Unexpanded usage in refine call.

[cjnolet]

Thank you for reporting this issue to us @shainotshy1. We get this fixed asap.