Fix "supposed" typo in ACME documentation.
Current limitations: The feature is limited to the HTTP-01 challenge for now.
The current HAProxy architecture is a non-blocking model, access to the disk is
-not suppose to be done after the configuration is loaded, because it could
+not supposed to be done after the configuration is loaded, because it could
block the event loop, blocking the traffic on the same thread. Meaning that the
certificates and keys generated from HAProxy will need to be dumped from
outside HAProxy using "dump ssl cert" on the stats socket.