librevisa: remove because its source is gone

The librevisa site and source code have disappeared upstream.

pkgs/development/libraries/librevisa/default.nix

···
-{ lib, stdenv, fetchurl, pkg-config, libusb1 }:
-
-# TODO: add VXI development files, for VXI-11 (TCPIP) support
-
-stdenv.mkDerivation rec {
-  pname = "librevisa";
-  version = "0.0.20130412";
-
-  src = fetchurl {
-    url = "http://www.librevisa.org/download/${pname}-${version}.tar.gz";
-    sha256 = "0bjzq23s3xzw0l9qx4l8achrx5id8xdd6r52lvdl4a28dxzbcfhq";
-  };
-
-  nativeBuildInputs = [ pkg-config ];
-  buildInputs = [ libusb1 ];
-
-  meta = with lib; {
-    description = "Implementation of the VISA standard (for instrument control)";
-    longDescription = ''
-      LibreVISA aims to be a compliant implementation of the VISA standard in a
-      free software library.
-
-      We currently support targets connected via USB, exposing the USBTMC
-      interface, and VXI-11 devices.
-    '';
-    homepage = "http://www.librevisa.org/";
-    license = licenses.gpl3Plus;
-    platforms = platforms.linux ++ platforms.darwin;
-    maintainers = [ maintainers.bjornfor ];
-  };
-}

pkgs/top-level/aliases.nix

···
   librdf = lrdf; # Added 2020-03-22
   librecad2 = throw "'librecad2' has been renamed to/replaced by 'librecad'"; # Converted to throw 2022-02-22
   libressl_3_2 = throw "'libressl_3_2' has reached end-of-life "; # Added 2022-03-19
+  librevisa = throw "librevisa has been removed because its website and source have disappeared upstream"; # Added 2022-09-23
   librsync_0_9 = throw "librsync_0_9 has been removed"; # Added 2021-07-24
   libseat = seatd; # Added 2021-06-24
   libspotify = throw "libspotify has been removed because Spotify stopped supporting it"; # added 2022-05-29

pkgs/top-level/all-packages.nix

···
 
   librevenge = callPackage ../development/libraries/librevenge {};
 
-  librevisa = callPackage ../development/libraries/librevisa { };
-
   librime = callPackage ../development/libraries/librime {
     boost = boost174;
   };