[Rust] Edit Rust README

[asfimport]

Issue automatically created from Pull Request 9576
Edits and fixes for some missing words, punctuation, and wording.

Reporter: Andrew Lamb / @alamb

PRs and other links:

• GitHub Pull Request #9576

_{Note: This issue was originally created as ARROW-11821. Please see the migration documentation for further details.}

[asfimport]

Andrew Lamb / @alamb:
Issue resolved by pull request 9576
#9576