pkgs: remove 'bt-migrate'

I have packaged it upstream.

pkgs/bt-migrate/default.nix

@@ -1,61 +0,0 @@
-{ lib
-, boost
-, cmake
-, cxxopts
-, digestpp
-, fetchFromGitHub
-, fmt
-, jsoncons
-, pugixml
-, sqlite_orm
-, stdenv
-}:
-stdenv.mkDerivation {
-  pname = "bt-migrate";
-  version = "0-unstable-2023-08-17";
-
-  src = fetchFromGitHub {
-    owner = "mikedld";
-    repo = "bt-migrate";
-    rev = "e15a489c0c76f98355586ebbee08223af4e9bf50";
-    hash = "sha256-kA6yxhbIh3ThmgF8Zyoe3I79giLVmdNr9IIrw5Xx4s0=";
-  };
-
-  nativeBuildInputs = [
-    cmake
-  ];
-
-  buildInputs = [
-    boost
-    cxxopts
-    fmt
-    jsoncons
-    pugixml
-    sqlite_orm
-  ];
-
-  cmakeFlags = [
-    (lib.strings.cmakeBool "USE_VCPKG" false)
-    # NOTE: digestpp does not have proper CMake packaging (yet?)
-    (lib.strings.cmakeBool "USE_FETCHCONTENT" true)
-    (lib.strings.cmakeFeature "FETCHCONTENT_SOURCE_DIR_DIGESTPP" "${digestpp}/include/digestpp")
-  ];
-
-  # NOTE: no install target in CMake...
-  installPhase = ''
-    runHook preInstall
-
-    mkdir -p $out/bin
-    cp BtMigrate $out/bin
-
-    runHook postInstall
-  '';
-
-  meta = with lib; {
-    description = "Torrent state migration tool";
-    homepage = "https://github.com/mikedld/bt-migrate";
-    license = licenses.gpl3Only;
-    maintainers = with maintainers; [ ambroisie ];
-    mainProgram = "BtMigrate";
-  };
-}

pkgs/default.nix

@@ -1,7 +1,5 @@
 { pkgs }:
 pkgs.lib.makeScope pkgs.newScope (pkgs: {
-  bt-migrate = pkgs.callPackage ./bt-migrate { };
-
   bw-pass = pkgs.callPackage ./bw-pass { };
 
   change-audio = pkgs.callPackage ./change-audio { };