[lldb][NFC] Remove a redundant call to weak_ptr::expired

[teemperor]

Summary

The lock call directly will check for us if the weak_ptr is expired and
returns an invalid shared_ptr (which we correctly handle), so this check is redundant.

[JDevlieghere]

LGTM

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

void SymbolFileDWARF::DumpClangAST(Stream &s) {
   TypeSystemClang *clang =
       llvm::dyn_cast_or_null<TypeSystemClang>(&ts_or_err.get());
   if (!clang)
     return;
   clang->Dump(s);
 }
 
 SymbolFileDWARFDebugMap *SymbolFileDWARF::GetDebugMapSymfile() {
-  if (m_debug_map_symfile == nullptr && !m_debug_map_module_wp.expired()) {
+  if (m_debug_map_symfile == nullptr) {
     lldb::ModuleSP module_sp(m_debug_map_module_wp.lock());
     if (module_sp) {
       m_debug_map_symfile =
           static_cast<SymbolFileDWARFDebugMap *>(module_sp->GetSymbolFile());
     }
   }
   return m_debug_map_symfile;
 }