README.md: remove incorrect link to openssl.github.io

The link to the OpenSSL Project Pages <openssl.github.io>
actually points to an unfinished draft <mspncp.github.io>.

The original intention of this pet project of mine was to
have a website dedicated to describing the OpenSSL workflow
on GitHub and to answer frequently asked questions related
to pull requests and the review process.

The progress on that project has stalled and I'm not so sure
anymore whether it is good idea to have yet another project
website. In particular since the OpenSSL Wiki has seen some
revival and increased activity caused by the upcoming
OpenSSL 3.0 release.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/12361)

README.md

@@ -156,11 +156,6 @@ Contributing
 If you are interested and willing to contribute to the OpenSSL project,
 please take a look at the [CONTRIBUTING](CONTRIBUTING.md) file.
 
-Since 2016, development takes place in public on the GitHub open source
-platform. The OpenSSL Project Pages at [openssl.github.io][] are a
-valuable source of information if you want to get familiar with our
-development process on GitHub.
-
 Legalities
 ==========
 
@@ -195,10 +190,6 @@ All rights reserved.
     <https://github.com/openssl/openssl>
     "OpenSSL GitHub Mirror"
 
-[openssl.github.io]:
-    <https://mspncp.github.io>
-    "OpenSSL Project Pages"
-
 [wiki.openssl.org]:
     <https://wiki.openssl.org>
     "OpenSSL Wiki"