[DOC] fix minor typo in the proxy protocol doc
As reported by David Swift, stunnel's option is "sendproxy".
diff --git a/doc/proxy-protocol.txt b/doc/proxy-protocol.txt
index c02fa5f..8d3ad83 100644
--- a/doc/proxy-protocol.txt
+++ b/doc/proxy-protocol.txt
@@ -146,7 +146,7 @@
easy to skip it from the input buffers.
We have a patch available for recent versions of Stunnel that brings it the
-ability to be an emitter. The feature is called "send-proxy" there. The code
+ability to be an emitter. The feature is called "sendproxy" there. The code
for the receiving side has been merged into haproxy and is enabled using the
"accept-proxy" keyword on a "bind" statement. Haproxy will use the transport
information from the PROXY protocol for logging, ACLs, etc... everywhere an