maintaining.html: Update location of Debian patch tracker

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
diff --git a/maintaining.html b/maintaining.html
index 5400c75..522154c 100644
--- a/maintaining.html
+++ b/maintaining.html
@@ -524,7 +524,7 @@
         and
         <a href="http://packages.debian.org/manpages-dev">http://packages.debian.org/manpages-dev</a>,
 	and downloading the Debian tarballs.
-        Or look at the web <a href="http://patch-tracker.debian.org/package/manpages">patchtracker</a>.
+        Or look at the web <a href="https://tracker.debian.org/pkg/manpages">patchtracker</a>.
     </p>
     <p>
         The following mail address reaches people with an interest in man pages at Debian: