el/dot-emacs.el: Remove `noip' from `LD_PRELOAD' list while running `man'.

Later versions of `man-db' install a `seccomp' filter to prevent stray
manpages from (among other stuff) doing network things.  This interacts
badly with `noip', which wants to fetch the list of network interfaces
at startup.  Since the `man-db' filter is strictly better than what
`noip' is doing, just turn off `noip' while running `man'.