docs: Remove <em> obfuscation on public mailing list addresses.

docs: Remove <em> obfuscation on public mailing list addresses.

Wrapping every character of an email address in <em> looks bizarre, and
makes it impossible to read the text.  Apparently Brian did this in 2003
to try and obfuscate email addresses and avoid spam.

Of course, mesa-*@lists.freedesktop.org are public mailing lists and
trivial to find on the internet.  So obfuscation buys us nothing
(assuming the <em> technique even works at all, which I doubt).

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Brian Paul <brianp@vmware.com>
LOLed-at-by: Matt Turner :)