[wwwdocs] readings.html - libre.adacore.com is gone

[Gerald Pfeifer]

...so adjust to where it redirects.

Applied.

Gerald

Index: readings.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/readings.html,v
retrieving revision 1.287
diff -u -r1.287 readings.html
--- readings.html       14 Dec 2017 01:10:53 -0000      1.287
+++ readings.html       8 Jan 2018 00:09:47 -0000
@@ -552,7 +552,7 @@
 
  <li>Other resources:
  <ul>
-   <li><a href="http://libre.adacore.com/";>AdaCore &mdash; Libre Site</a></li>
+   <li><a href="https://www.adacore.com/community";>AdaCore Community 
Site</a></li>
    <li><a href="https://www2.adacore.com/gap-static/GNAT_Book/html/";>GNAT:
    The GNU Ada Compiler</a></li>
    <li><a 
href="http://www.adaic.org/resources/add_content/docs/95style/html/cover.html";>Ada