nginxMainline: 1.21.5 -> 1.21.6

pkgs/servers/http/nginx/mainline.nix

···
 { callPackage, openssl_3_0, ... }@args:
 
 callPackage ./generic.nix (args // { openssl = openssl_3_0; }) {
-  version = "1.21.5";
-  sha256 = "sha256-sg879TOlGKbw86eWff7thy0mjTHkzBIaAAEylgLdz7s=";
+  version = "1.21.6";
+  sha256 = "1bh52jqqcaj5wlh2kvhxr00jhk2hnk8k97ki4pwyj4c8920p1p36";
 }