clang-format: Indent from dict literal labels.

Before:
  @{
    NSFontAttributeNameeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee :
    regularFont,
  };

After:
  @{
    NSFontAttributeNameeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee :
        regularFont,
  };

llvm-svn: 204041