remove 'overlay' folder

overlay/default.nix

@@ -1,4 +0,0 @@
-self: super: {
-  studio-link = super.callPackage ./studio-link.nix { };
-
-}

overlay/studio-link.nix

@@ -1,40 +0,0 @@
-{ stdenv
-, lib
-, fetchurl
-, pulseaudio
-, zlib
-, alsaLib
-, autoPatchelfHook
-}:
-
-stdenv.mkDerivation rec {
-  pname = "studio-link";
-  version = "21.07.0";
-
-  src = fetchurl {
-    url = "https://download.studio.link/releases/v${version}-stable/linux/studio-link-standalone-v${version}.tar.gz";
-    hash = "sha256-4CkijAlenhht8tyk3nBULaBPE0GBf6DVII699/RmmWI=";
-  };
-
-  sourceRoot = ".";
-
-  nativeBuildInputs = [
-    autoPatchelfHook
-  ];
-  
-  buildInputs = [
-    alsaLib
-    pulseaudio
-    zlib
-  ];
-  
-  installPhase = ''
-    install -D -m755 studio-link-standalone-v* $out/bin/studio-link
-  '';
-
-  meta = with lib; {
-    homepage = "https://studio-link.com";
-    description = "VoIP Thing";
-    platforms = platforms.linux;
-  };
-}