Remove deprecated sudoers checks

It would seem that the checks made by `rvmsudo` against the `/etc/sudoers` file had already previously been rendered unnecessary by the inclusion of a subshell in the `sudo` command, which *always* (regardless of the `/etc/sudoers` checks) makes a call to `env` with an `awk` script to force all the required environment variables through. After my edits, this is seen in lines 34-39 of the file.

The *additional* prefixing of `env` does not appear to be necessary, as the subshell *always* pushes the environment variables anyway. So on my Ubuntu system where `/etc/sudoers` is readable only by root, and in addition has `secure_path` enabled, this modified version a) doesn't produce a warning, and b) works just fine - $PATH, as well as the other vrm/ruby environment variables pass through alright.

Am I wrong? Is the *additional* prefixing of `env` required for some specific reason I'm not seeing?