docs: correct grammar in docs/Overview/KeyConcepts.md

[jeffschaper]

⚠️   Pre Checklist

Please complete ALL items in this checklist, and remove before submitting

• I have npm run build and npm run serve locally before submitting this PR
• I have read through the Contributing Documentation

Summary

• I updated the wording in the docs/Overview/KeyConcepts#transformations section, but didn't update the versioned docs since it isn't clear how a patch like this cascades down to versioned docs.
• My editor also removed trailing whitespace in a few areas.

Does this close any open issues?

Nope

Screenshots

Include any relevant screenshots here.

Other Information

Any other information that is important to this PR.

[klesh]

Thanks for your contribution