It is not an option to remove it. You would need to use a 3rd party form builder that doesn't require it. We found that without them there were too many spam bots flooding forms with responses. Not only does this become annoying to the end user, it also causes problems with spam filters.
It would be nice to possibly have an option to remove the 'I'm not a robot' feature in the future. As daft as it may sound people can sometimes be deterred from completing an inquiry form when having to start clicking elements to prove they are not a robot.
Fair play though as we're lucky and don't have any issues with spam via the contact form. What I will say though is although I couldn't say 100% I'm fairly certain I have seen enquiries drop of a little via the contact form since this feature was introduced.