libstdc++: Refer to Git documentation

	* doc/xml/manual/appendix_contributing.xml: Refer to Git
	documentation instead of Subversion.  Switch to https.
	* doc/html/manual/appendix_contributing.html: Regenerate.

libstdc++-v3/ChangeLog

+2020-04-05  Gerald Pfeifer  <gerald@pfeifer.com>
+
+	* doc/xml/manual/appendix_contributing.xml: Refer to Git
+	documentation instead of Subversion.  Switch to https.
+	* doc/html/manual/appendix_contributing.html: Regenerate.
+
 2020-04-03  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/93960

libstdc++-v3/doc/html/manual/appendix_contributing.html

@@ -68,7 +68,7 @@
       <code class="email">&lt;<a class="email" href="mailto:assign@gnu.org">assign@gnu.org</a>&gt;</code>, please CC the libstdc++
       maintainers above so that progress can be monitored.
     </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="list.getting"></a>Getting Sources</h3></div></div></div><p>
-      <a class="link" href="http://gcc.gnu.org/svnwrite.html" target="_top">Getting write access
+      <a class="link" href="https://gcc.gnu.org/gitwrite.html" target="_top">Getting write access
 	(look for "Write after approval")</a>
     </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="list.patches"></a>Submitting Patches</h3></div></div></div><p>
       Every patch must have several pieces of information before it can be

libstdc++-v3/doc/xml/manual/appendix_contributing.xml

@@ -126,7 +126,7 @@
   <section xml:id="list.getting"><info><title>Getting Sources</title></info>
     
     <para>
-      <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://gcc.gnu.org/svnwrite.html">Getting write access
+      <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://gcc.gnu.org/gitwrite.html">Getting write access
 	(look for "Write after approval")</link>
     </para>
   </section>