buffet: Help string corrected to UpdateState

TEST=built
BUG=none

Change-Id: Ia90a9718153beeba4340b3deda1fbee11c78d0f3
Reviewed-on: https://chromium-review.googlesource.com/239180
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Nathan Bullock <nathanbullock@google.com>
Tested-by: Nathan Bullock <nathanbullock@google.com>

buffet/buffet_client.cc

diff --git a/buffet/buffet_client.cc b/buffet/buffet_client.cc
index ca91cee..0fa3f58 100644
--- a/buffet/buffet_client.cc
+++ b/buffet/buffet_client.cc
@@ -39,7 +39,7 @@
   - GetDeviceInfo
   - RegisterDevice param1=val1&param2=val2...
   - AddCommand '{"name":"command_name","parameters":{}}'
-  - UpdateStateMethod prop_name prop_value
+  - UpdateState prop_name prop_value
   - PendingCommands
 )");
 }