/embed URL after domain

Hi,

I created the following contact page,
https://stylusdesign.co.jp/contact/

but I didn’t intentionally create the following one,
https://stylusdesign.co.jp/contact/embed/

Both of them are accessible. I have no idea how I got that URL, what created it… and it shows up on WebPageTest.org result so I guess it negatively affects site’s performance or speed. Is it ok to leave it as it is or should I somehow remove it? Please advise what to do with it.

The page I need help with: [log in to see the link]