[th/wwan-ppp-no-gte-dns] wwan: drop workaround to use GTE DNS servers for PPP
Drop a workaround added by commit a8ca7f53 ('ppp: work around PPP bug that returns bogus nameservers'), in 2009.
Also drop the second workaround (if (!num ...
), which was introduced
by commit 294a5e31 ('modem: substitute known-good nameservers if PPP
doesn't return any (lp:434477)').
I hope this doesn't break something, but it really doesn't seem right in 2021.