[103 ObjC] TypographyScheme comment references ColorScheme

[romoore]

The TypographyScheme initialization comment on Line 78 of ApplicationScheme.m refers to an MDCSemanticColorScheme object.

 // Instantiate a MDCSemanticColorScheme object and modify it to our chosen colors
    _typographyScheme =
        [[MDCTypographyScheme alloc] initWithDefaults:MDCTypographySchemeDefaultsMaterial201804];

The bug seems to originate in the instructions, which have the wrong wording as well.

https://codelabs.developers.google.com/codelabs/mdc-103-objc/index.html?index=..%2F..index#3