[latexrefman] Suggestion for update url links

[Pablo González L]

> Hi Pablo - Browsers should not complain. That is horrible behavior.
Unfortunately Google rules on many mobile devices and it seems to be
part of their new policy
(https://security.googleblog.com/2019/10/no-more-mixed-messages-about-https_3.html)
(https://developers.google.com/search/blog/2019/10/updating-user-agent-of-googlebot)

> In any case, sorry, I can't commit to spending time looking into
> changing non-broken links. If you or anyone feels like sending a patch,
> that would be fine. --thanks, karl.
The `.texi` format is a bit strange for me, and I think I have
forgotten how to work with `svn` :(