debianqueued: Do not output signature validity

Default GPG signature verification output has a trailing validity
identifier ("[ultimate]", "[unknown]", etc) now, so the gpg signature
checking regex was no longer matching. This resulted in surprising log
lines like:

Feb 29 04:59:31 processing /kees-1582951501.dak-commands
Feb 29 04:59:31 (PGP/GnuPG signature by unknown signator)

Existing regex is:
  $output =~ /^(gpg: )?good signature from (user )?"(.*)"\.?$/im;

Current gpg sees:

$ gpg --verify --no-default-keyring --keyring /srv/keyring.debian.org/keyrings/debian-keyring.gpg kees-1582951501.dak-commands
gpg: Signature made Sat 29 Feb 2020 04:45:01 AM UTC
gpg:                using RSA key A5C3F68F229DD60F723E6E138972F4DFDC6DC026
gpg: Good signature from "Kees Cook <kees@outflux.net>" [unknown]
gpg:                 aka "Kees Cook <kees@debian.org>" [unknown]
...

Instead, launch gpg with --verify-options no-show-uid-validity to avoid
breaking the regex.

While here, I made the more robust by adding "?:" prefixes to the unused
regex match groups so the assignment on the next line can always use $1:

  ( $signator = $1 ) ||= "unknown signator";

tools/debianqueued-0.9/debianqueued

@@ -1672,6 +1672,7 @@ sub pgp_check($) {
     my @command = ("$conf::gpg", "--no-options", "--batch", "--no-tty",
                    "--trust-model", "always", "--no-default-keyring",
 		   (map +("--keyring" => $_), @conf::keyrings),
+		   "--verify-options", "no-show-uid-validity",
 		   "--verify", "-");
     debug(   "executing " . join(" ", @command) );
 
@@ -1706,8 +1707,8 @@ sub pgp_check($) {
     return "";
   } ## end if ($stat)
 
-  $output =~ /^(gpg: )?good signature from (user )?"(.*)"\.?$/im;
-  ( $signator = $3 ) ||= "unknown signator";
+  $output =~ /^(?:gpg: )?good signature from (?:user )?"(.*)"\.?$/im;
+  ( $signator = $1 ) ||= "unknown signator";
   if ($conf::debug) {
     debug("GnuPG signature ok (by $signator)");
   }