libgit2_0_21: remove, unused and probably vulnerable

pkgs/development/libraries/git2/0.21.nix

@@ -1,24 +0,0 @@
-{stdenv, fetchurl, cmake, zlib, python, libssh2, openssl, http-parser}:
-
-stdenv.mkDerivation rec {
-  version = "0.21.2";
-  name = "libgit2-${version}";
-
-  src = fetchurl {
-    name = "${name}.tar.gz";
-    url = "https://github.com/libgit2/libgit2/tarball/v${version}";
-    sha256 = "0icf119lhha96rk8m6s38sczjr0idr7yczw6knby61m81a25a96y";
-  };
-
-  cmakeFlags = "-DTHREADSAFE=ON";
-
-  nativeBuildInputs = [ cmake python ];
-  buildInputs = [ zlib libssh2 openssl http-parser ];
-
-  meta = {
-    description = "The Git linkable library";
-    homepage = http://libgit2.github.com/;
-    license = stdenv.lib.licenses.gpl2;
-    platforms = with stdenv.lib.platforms; all;
-  };
-}