[build] OHHTTPStubs out of date in Cartfile

[garvankeeley]

*** Skipped installing OHHTTPStubs.framework binary due to the error:
	"Incompatible Swift version - framework was built with 3.0.1 (swiftlang-800.0.58.6 clang-800.0.42.1) and the local version is 4.0 (swiftlang-900.0.65 clang-900.0.37)."