[From Zendesk] Squash and merge mention in commit signing article now incorrect

[docs-bot]

Issue overview

We now sign commits that are created via squashing a merging a pull request: https://github.blog/changelog/2019-12-19-improved-attribution-when-squashing-commits/

GitHub will automatically use GPG to sign commits you make using the GitHub web interface, except for when you squash and merge a pull request that you are not the author of.

— https://help.github.com/en/github/authenticating-to-github/about-commit-signature-verification

This statement is no longer true 👆

Let's remove this part of the sentence:

except for when you squash and merge a pull request that you are not the author of.