graphql-ruby: Fix tests, grammar fixes, rewording

[jcat4]

This change does 2 main things:

1. Fix tests

This is the same issue as #1431. The code was not splatting hash arguments being passed to functions expecting keyword arguments.

2. Small rewording, grammar and punctuation fixes

There was a small grammar error, a run-on sentence, and one explanation that I felt could be worded a little more clearly.