Docs: fix wording in configuring.md

[piperchester]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[x] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

What changes did you make? (Give an overview)

Micro wording fix in a doc.

Is there anything you'd like reviewers to focus on?

Nope!

[jsf-clabot]

All committers have signed the CLA.

[nzakas]

Thanks for the pull requests. There is, indeed, a plural form mismatch to fix.

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Thanks!

[piperchester]

Thanks for the pull requests. There is, indeed, a plural form mismatch to fix.

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Thanks!

Thanks! Done :-)

[nzakas]

LGTM. Thanks!