In RFC 7233, response body size of range requests with parameter
'bytes=N-M' is (M - N + 1). And response of object GET request with
range parameter in current Swift implementation is according to the
RFC. However, in current api reference explains that response body
size of object GET request with 'Range: bytes=10-15' is five
( != 15 - 10 + 1).
This patch fixes the api reference explanation.
Change-Id: I8371864f8e5adb42c1e56b7ea26c556ea1252728