Follow up of doc strings pattern

[spolti]

From https://github.com/kserve/modelmesh-runtime-adapter/pull/68/files#r1403679093:

If we update the function doc strings, we should make sure they read correctly, i.e. lower case the word "Returns" here. Same for the changed doc strings below.

As you mentioned, we could do a sweep in a separate PR, to fix the doc comment grammar, but I don't think that would get picked up since there is always more important work to do :-)

I would either leave these doc changes out of this PR, so at least they read well. Or, in this PR, fix the grammar to bring it up to style as in the examples here: https://www.digitalocean.com/community/tutorials/how-to-write-comments-in-go#doc-comments