chore(app): keep only avcpp variant

nix/mosh-me.nix

@@ -5,14 +5,13 @@
   spdlog,
   stdenv,
   pkg-config,
-  ffmpeg_7,
   avcpp,
 }:
 stdenv.mkDerivation (finalAttrs: {
   name = "mosh-me";
   src = ../.;
   nativeBuildInputs = [cmake ninja pkg-config];
-  buildInputs = [ffmpeg_7 spdlog avcpp];
+  buildInputs = [spdlog avcpp];
   cmakeFlags = [
     (lib.cmakeBool "BUILD_TESTING" finalAttrs.doCheck)
   ];