MINOR: spoe: Remove useless 'timeout ack' option

To limit the time to process an event, you should set 'timeout processing'
option. So 'timeout ack' option is redundant and useless.
diff --git a/contrib/spoa_example/README b/contrib/spoa_example/README
index 3494256..7e376ee 100644
--- a/contrib/spoa_example/README
+++ b/contrib/spoa_example/README
@@ -36,9 +36,9 @@
 
         option var-prefix iprep
 
-        timeout hello   1s
-        timeout ack     10ms
-        timeout idle    30s
+        timeout hello      100ms
+        timeout idle       30s
+        timeout processing 15ms
 
         use-backend iprep-backend