Fix translation in recaptcha.md

What does this MR do and why?

Fix some translation in recaptcha.md to make it more clear

Screenshots or screen recordings

How to set up and validate locally

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

/cc @mtan-gitlab-cn