DOC: peers: fix the protocol tag name in the doc

The peers protocol has been using "HAProxyS" as a binary tag sent on the
wire since day one in 1.5-dev3 with commit 2b920a1af ("[MAJOR] Add new
files src/peer.c, include/proto/peers.h and include/types/peers.h for
sync stick table management"), regardless, the doc says the protocol
identifier is "HaproxyS". It is likely this got fixed in the code before
merging and not in the doc.

This should be backported to any release as the doc is wrong.
diff --git a/doc/peers-v2.0.txt b/doc/peers-v2.0.txt
index af2bc37..5f3aa11 100644
--- a/doc/peers-v2.0.txt
+++ b/doc/peers-v2.0.txt
@@ -1,4 +1,4 @@
-	Haproxy's peers v2.0 protocol 08/18/2016
+	HAProxy's peers v2.0 protocol 08/18/2016
 
 Author: Emeric Brun ebrun@haproxy.com
 
@@ -36,7 +36,7 @@
 <remotepeerid>
 <localpeerid> <processpid> <relativepid>
 
-protocol: current value is "HaproxyS"
+protocol: current value is "HAProxyS"
 version: current value is "2.0"
 remotepeerid: is the name of the target peer as defined in the configuration peers section.
 localpeerid: is the name of the local peer as defined on cmdline or using hostname.