BinaryProtocol.md: Fix opcode number of Observe in title
BinaryProtocol.md: Fix opcode number of Observe in title

Change-Id: I873cd7a9398aaeb44d57efa00b450fe75785356b
Reviewed-on: http://review.couchbase.org/113193
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@couchbase.com>
Tested-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@couchbase.com>

daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine