[NFC][lldb] Remove duplicated checks (llvm#169093)

Removed duplicated checks reported by cppcheck

Author: DrSergei

lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp

@@ -199,9 +199,6 @@ lldb::ChildCacheState VectorIteratorSyntheticFrontEnd::Update() {
   if (!valobj_sp)
     return lldb::ChildCacheState::eRefetch;
 
-  if (!valobj_sp)
-    return lldb::ChildCacheState::eRefetch;
-
   ValueObjectSP item_ptr =
       formatters::GetChildMemberWithName(*valobj_sp, m_item_names);
   if (!item_ptr)

lldb/source/Plugins/Language/ObjC/NSSet.cpp

@@ -417,8 +417,6 @@ lldb_private::formatters::NSSetISyntheticFrontEnd::Update() {
   m_data_64 = nullptr;
   m_ptr_size = 0;
   ValueObjectSP valobj_sp = m_backend.GetSP();
-  if (!valobj_sp)
-    return lldb::ChildCacheState::eRefetch;
   if (!valobj_sp)
     return lldb::ChildCacheState::eRefetch;
   m_exe_ctx_ref = valobj_sp->GetExecutionContextRef();