Remove pam_script.so docs from SSH PAM page
Remove pam_script.so docs from SSH PAM page

With #3725 we now populate teleport-specific env vars in a way that's
accessible to `pam_exec.so`. There's no longer any reason to install
pam_script.so separately and duplicate our docs.

Updates #3692

gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport