Fix the parsing error for Carthage example.
Fix the parsing error for Carthage example.

Cathage seems to allow only `"` not `'` as a quote in the syntax.
And also, Carthage made by swift, that's why to change the syntax highlight for Carthage example.

https://github.com/Carthage/Carthage/blob/master/Source/CarthageKit/Cartfile.swift#L190
ReactorKit/ReactorKit,ReactorKit/ReactorKit