[lldb] Remove lldbassert from DebugNamesDWARFIndex::GetGlobalVariables

34a8e6e changed SymbolFileDWARF::GetDwoNum to
SymbolFileDWARF::GetFileIndex but changed the meaning from just DWO to
DWO and OSO which changed the meaning of the assert. The assert was
therefore removed from ManualDWARFIndex::GetGlobalVariables and
ManualDWARFIndex::GetGlobalVariables but was still present in
DebugNamesDWARFIndex::GetGlobalVariables. If we want to reintroduce the
assert, we need something with the old semantics for all 3.

Author: JDevlieghere

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

@@ -126,7 +126,6 @@ void DebugNamesDWARFIndex::GetGlobalVariables(
 
 void DebugNamesDWARFIndex::GetGlobalVariables(
     DWARFUnit &cu, llvm::function_ref<bool(DWARFDIE die)> callback) {
-  lldbassert(!cu.GetSymbolFileDWARF().GetFileIndex());
   uint64_t cu_offset = cu.GetOffset();
   bool found_entry_for_cu = false;
   for (const DebugNames::NameIndex &ni: *m_debug_names_up) {