Revert "nixos/malloc: add back maybe unnecessary line"

This reverts commit ed55524562e14131250b8362f47ccfe2d6e5a328.

Does not evaluate.

nixos/modules/config/malloc.nix

···
   };
 
   config = mkIf (cfg.provider != "libc") {
-    boot.kernel.sysctl."vm.max_map_count" = mkIf (cfg.provider == "graphene-hardened") (mkDefault 1048576); # TODO: Default vm.max_map_count has been increased system-wide
     environment.etc."ld-nix.so.preload".text = ''
       ${providerLibPath}
     '';