gpg: Do not print a hint to use the deprecated --keyserver option.

gpg: Do not print a hint to use the deprecated --keyserver option.

* g10/keyserver.c (keyserver_search): Remove a specialized error
message.
--

Dirmngr comes with a default keyserver and the suggestion to use
gpg --keyserver
is not good because that option is deprecated.  An error message
"No keyserver available" is sufficient.

GnuPG-bug-id: 4512
Signed-off-by: Werner Koch <wk@gnupg.org>
(cherry picked from commit 8d645f1d1f2b0f4e2d3b72f2a585acac4bdd8846)

Gbp-Pq: Topic from-2.2.16
Gbp-Pq: Name gpg-Do-not-print-a-hint-to-use-the-deprecated-keyserver-o.patch