doc: update LICENSE file

Running `license-builder.sh` seems to indicate that there have been some
license changes that have not been propagated to our LICENSE file yet.
Here they are.

PR-URL: https://github.com/nodejs/node/pull/21472
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>

LICENSE

@@ -93,11 +93,7 @@ The externally maintained libraries used by Node.js are:
 
 - HTTP Parser, located at deps/http_parser, is licensed as follows:
   """
-    http_parser.c is based on src/http/ngx_http_parse.c from NGINX copyright
-    Igor Sysoev.
-
-    Additional changes are licensed under the same terms as NGINX and
-    copyright Joyent, Inc. and other Node contributors. All rights reserved.
+    Copyright Joyent, Inc. and other Node contributors.
 
     Permission is hereby granted, free of charge, to any person obtaining a copy
     of this software and associated documentation files (the "Software"), to
@@ -612,7 +608,7 @@ The externally maintained libraries used by Node.js are:
 
 - OpenSSL, located at deps/openssl, is licensed as follows:
   """
-    Copyright (c) 1998-2017 The OpenSSL Project.  All rights reserved.
+    Copyright (c) 1998-2018 The OpenSSL Project.  All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
@@ -715,6 +711,9 @@ The externally maintained libraries used by Node.js are:
       - Valgrind client API header, located at third_party/valgrind/valgrind.h
         This is release under the BSD license.
 
+      - antlr4 parser generator Cpp library located in third_party/antlr4
+        This is release under the BSD license.
+
     These libraries have their own licenses; we recommend you read them,
     as their terms may differ from the terms below.