nix-search-tv: add missing environment variable (#447307)

Changed files
+2
pkgs
by-name
ni
nix-search-tv
+2
pkgs/by-name/ni/nix-search-tv/package.nix
···
subPackages = [ "cmd/nix-search-tv" ];
+
env.GOEXPERIMENT = "jsonv2";
+
ldflags = [
"-s"
"-w"