[lldb][gardening] Remove full name of "DWARFDIE" type in GetTypeForDIE (#70062)

When moving the GetTypeForDIE function from DWARFASTParserClang to
DWARFASTParser, I kept the signature as-is. To match the rest of the
function signatures in DWARFASTParser, remove the full name
(lldb_private::plugin::dwarf::DWARFDIE -> DWARFDIE) in the signature of
DWARFASTParser::GetTypeForDIE.