Use generic captcha form element in email password reset form

What does this MR do and why?

Fix problem after replacing tencent captcha to geetest captcha.

Fixes #2800 (closed)

Limitation

TODO: reCaptcha (enabled when tencent captcha and geetest captcha are disabled) is not supported here. Following issue in

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

Enable captcha check like https://docs.gitlab.com/ee/integration/recaptcha.html

Enable tencent replacement of captcha

Feature.enable(:tencent_captcha)

and test tencent captcha

Enable geetest replacement of captcha

Feature.enable(:geetest_captcha)

and test geetest captcha

Numbered steps to set up and validate the change are strongly suggested.

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.