remove obsolete stdenv darwinMinVersion override

we are more up-to-date now:

nix-repl> stdenv.hostPlatform.darwinMinVersion
"11.3"

flake.nix

@@ -170,7 +170,7 @@
               {
                 otherSplices = final.generateSplicesForMkScope "nixDependencies";
                 f = import ./packaging/dependencies.nix {
-                  inherit inputs stdenv;
+                  inherit stdenv;
                   pkgs = final;
                 };
               };

packaging/dependencies.nix

@@ -1,33 +1,14 @@
 # These overrides are applied to the dependencies of the Nix components.
 
 {
-  # Flake inputs; used for sources
-  inputs,
-
   # The raw Nixpkgs, not affected by this scope
   pkgs,
 
   stdenv,
 }:
 
-let
-  prevStdenv = stdenv;
-in
-
 let
   inherit (pkgs) lib;
-
-  stdenv = if prevStdenv.isDarwin && prevStdenv.isx86_64 then darwinStdenv else prevStdenv;
-
-  # Fix the following error with the default x86_64-darwin SDK:
-  #
-  #     error: aligned allocation function of type 'void *(std::size_t, std::align_val_t)' is only available on macOS 10.13 or newer
-  #
-  # Despite the use of the 10.13 deployment target here, the aligned
-  # allocation function Clang uses with this setting actually works
-  # all the way back to 10.6.
-  darwinStdenv = pkgs.overrideSDK prevStdenv { darwinMinVersion = "10.13"; };
-
 in
 scope: {
   inherit stdenv;