librdf_redland: remove unused pcre dependency

pcre 1 is deprecated and should not be used.
`librdf_redland` previously offered optional pcre 1 support,
but has since completely removed that dependency.
Comparing build artifacts with and without pcre 1 using diffoscope,
the output is identical (apart from references to the $out nix store paths).

pkgs/development/libraries/librdf/redland.nix

@@ -7,7 +7,6 @@
   libxslt,
   perl,
   curl,
-  pcre,
   libxml2,
   librdf_rasqal,
   gmp,
@@ -40,7 +39,6 @@ stdenv.mkDerivation rec {
       openssl
       libxslt
       curl
-      pcre
       libxml2
       gmp
     ]