docs/website: fix the link to the mailman archives

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit b07ee5e41c806138dd8d214b842dabdb802dd64f)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/website/support.html

@@ -53,7 +53,7 @@
 		    page</a>.  Only subscribers to the Buildroot
 		    mailing list are allowed to post to this
 		    list. Archives are available
-		    from <a href="/lists/buildroot/">Mailman</a>
+		    from <a href="https://lists.buildroot.org/pipermail/buildroot/">Mailman</a>
 		    and <a href="https://lore.kernel.org/buildroot/">lore.kernel.org</a>.
 
 		  <h4>Search the List Archives</h4>