Update license boilerplate.

The boilerplate included attribution to NGINX that created confusion
because NGINX is distributed under a different license (BSD, not MIT.)

To the best of everyone's knowledge, no actual NGINX code remains.
Remove the attribution to clear up the confusion.

Fixes: https://github.com/nodejs/http-parser/issues/389
PR-URL: https://github.com/nodejs/http-parser/pull/390
Reviewed-By: Fedor Indutny <fedor@indutny.com>

LICENSE-MIT

@@ -1,8 +1,4 @@
-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

contrib/parsertrace.c

@@ -1,7 +1,4 @@
-/* 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

http_parser.c

@@ -1,7 +1,4 @@
-/* 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