Minor grammar fixes in the developers documentation

[zbraiterman]

What does this PR fix/introduce?

// Add a brief description or bullet points about the changes introduced. // Include an issue number that is associated with this PR.

Closes #

Additional context

// Add further detail on the current situation, or what the PR seeks to address. // Include loom, screenshots, or gifs(record, compress) if helpful.

Checklist

(Delete any that aren't relevant)

• [ * ] Docs are successfully building - yarn install && yarn run build.
• [ * ] For new internal links I used relative file paths (with .md extension) - e.g. ../../faq/faq-general.md - instead of introducing absolute file path, or relative/absolute URL.
• [ * ] All external links have been verified with yarn run check:externals.
• [ * ] My changes follow the Casper docs style guidelines.
• [ * ] All technical procedures have been tested (if you want help with this, mention it in Reviewers).
• [ * ] If structural changes are introduced (not just content changes), cross-browser testing has been completed.

Reviewers

// Tag whoever needs to review. If you're not sure, leave blank.