[RELEASE] Released version 2.3.9

Released version 2.3.9 with the following main changes :
    - BUG/MEDIUM: mux-h1: make h1_shutw_conn() idempotent
    - MEDIUM: backend: use a trylock to grab a connection on high FD counts as well
    - BUG/MINOR: payload: Wait for more data if buffer is empty in payload/payload_lv
    - BUG/MINOR: stats: Apply proper styles in HTML status page.
    - BUG/MEDIUM: time: make sure to always initialize the global tick
diff --git a/doc/configuration.txt b/doc/configuration.txt
index a426438..c0fed55 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -4,7 +4,7 @@
                          ----------------------
                               version 2.3
                              willy tarreau
-                              2021/03/25
+                              2021/03/30
 
 
 This document covers the configuration language as implemented in the version