DOC: remove my name from the config doc

I was surprised to notice that my name was still present as the author
at the top of the config manual. It turns out that this line and a few
other ones in this file remained unchanged since commit 6a06a40501 that
added this doc 15 years ago! It's long been time to get rid of this!
diff --git a/doc/configuration.txt b/doc/configuration.txt
index 1acc560..16c23fb 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -3,7 +3,6 @@
                           Configuration Manual
                          ----------------------
                               version 2.6
-                             willy tarreau
                               2022/04/16