Update textstyles on home.dart

[adoankim]

Updating textstyles on home.dart by replacing deprecated textThemes with the new ones :)

Edit: I guess the codelab textstyle related instructions should be updated too? 🤔 . However haven't found where they are.

TextTheme _buildShrineTextTheme(TextTheme base) {
  return base.copyWith(
    headline: base.headline.copyWith(
      fontWeight: FontWeight.w500,
    ),
    title: base.title.copyWith(
        fontSize: 18.0
    ),
    caption: base.caption.copyWith(
      fontWeight: FontWeight.w400,
      fontSize: 14.0,
    ),
  ).apply(
    fontFamily: 'Rubik',
    displayColor: kShrineBrown900,
    bodyColor: kShrineBrown900,
  );
}

To

TextTheme _buildShrineTextTheme(TextTheme base) {
  return base
      .copyWith(
        headline5: base.headline5.copyWith(
          fontWeight: FontWeight.w500,
        ),
        headline6: base.headline6.copyWith(fontSize: 18.0),
        caption: base.caption.copyWith(
          fontWeight: FontWeight.w400,
          fontSize: 14.0,
        ),
      )
      .apply(
        fontFamily: 'Rubik',
        displayColor: kShrineBrown900,
        bodyColor: kShrineBrown900,
      );
}

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[adoankim]

@googlebot I signed it!

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