doc: txt2pre: linkify -extindex(1), dedupe -config(5)

I noticed the HTML manpages didn't have -extindex linkification
while checking over the docs.  While adding it, I also noticed
-config(5) had two entries :x

diff --git a/Documentation/txt2pre b/Documentation/txt2pre
index 89a77199074cd91423c08bef199700c110398fe6..b45c52e8ba2494ea52ed5d800c580688417cd534 100755 (executable)
--- a/Documentation/txt2pre
+++ b/Documentation/txt2pre
@@ -53,10 +53,10 @@ for (qw[lei(1)
        public-inbox-cindex(1)
        public-inbox-clone(1)
        public-inbox-config(5)
-       public-inbox-config(5)
        public-inbox-convert(1)
        public-inbox-daemon(8)
        public-inbox-edit(1)
+       public-inbox-extindex(1)
        public-inbox-fetch(1)
        public-inbox-glossary(7)
        public-inbox-httpd(1)