lean2: remove after being marked broken for over two years

It was marked in commit 5aa4b19946 by Linus Heckemann on 2019-10-07 (commited on 2019-10-08)

pkgs/applications/science/logic/lean2/default.nix

@@ -1,37 +0,0 @@
-{ lib, stdenv, fetchFromGitHub, cmake, gmp, mpfr, python2
-, gperftools, ninja, makeWrapper }:
-
-stdenv.mkDerivation {
-  pname = "lean2";
-  version = "2017-07-22";
-
-  src = fetchFromGitHub {
-    owner  = "leanprover";
-    repo   = "lean2";
-    rev    = "34dbd6c3ae612186b8f0f80d12fbf5ae7a059ec9";
-    sha256 = "1xv3j487zhh1zf2b4v19xzw63s2sgjhg8d62a0kxxyknfmdf3khl";
-  };
-
-  nativeBuildInputs = [ cmake makeWrapper ninja ];
-  buildInputs = [ gmp mpfr python2 gperftools ];
-
-  preConfigure = ''
-    patchShebangs bin/leantags
-    cd src
-  '';
-
-  cmakeFlags = [ "-GNinja" ];
-
-  postInstall = ''
-    wrapProgram $out/bin/linja --prefix PATH : $out/bin:${ninja}/bin
-  '';
-
-  meta = with lib; {
-    description = "Automatic and interactive theorem prover (version with HoTT support)";
-    homepage    = "http://leanprover.github.io";
-    license     = licenses.asl20;
-    platforms   = platforms.unix;
-    maintainers = with maintainers; [ thoughtpolice gebner ];
-    broken = true;
-  };
-}

pkgs/top-level/all-packages.nix

@@ -32805,7 +32805,6 @@ with pkgs;
   keymapviz = callPackage ../tools/misc/keymapviz { };
 
   lean = callPackage ../applications/science/logic/lean {};
-  lean2 = callPackage ../applications/science/logic/lean2 {};
   lean3 = lean;
   elan = callPackage ../applications/science/logic/elan {};
   mathlibtools = with python3Packages; toPythonApplication mathlibtools;