Update name of objc runtime SPI function we call for class names.

A new SPI was added to the objc runtime to get class names without
any demangling; AppleObjCRuntimeV2::ParseClassInfoArray was using
the original prototype name but had not been updated for the final
name yet, so lldb was falling back to the old function and doing
extra work for classes that were demangled.  This commit fixes that.

llvm-svn: 370152