This wasn't defined correctly and was unused. And it was causing a CI
build failure:
```
/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu-dwarf5/llvm-project/lldb/include/lldb/Core/DemangledNameInfo.h: In function ‘bool lldb_private::operator==(const lldb_private::DemangledNameInfo&, const lldb_private::DemangledNameInfo&)’:
/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu-dwarf5/llvm-project/lldb/include/lldb/Core/DemangledNameInfo.h:60:25: error: ‘const struct lldb_private::DemangledNameInfo’ has no member named ‘QualifiersRange’
60 | lhs.QualifiersRange) ==
| ^~~~~~~~~~~~~~~
/home/buildbot/buildbot-root/cross-project-tests-sie-ubuntu-dwarf5/llvm-project/lldb/include/lldb/Core/DemangledNameInfo.h:62:25: error: ‘const struct lldb_private::DemangledNameInfo’ has no member named ‘QualifiersRange’
62 | lhs.QualifiersRange);
| ^~~~~~~~~~~~~~~
111.469 [1284/7/3896] Building CXX object tools/lldb/source/Expression/CMakeFiles/lldbExpression.dir/ObjectFileJIT.cpp.o
111.470 [1284/6/3897] Building CXX object tools/lldb/source/Expression/CMakeFiles/lldbExpression.dir/Materializer.cpp.o
111.492 [1284/5/3898] Building CXX object tools/lldb/source/Expression/CMakeFiles/lldbExpression.dir/REPL.cpp.o
111.496 [1284/4/3899] Building CXX object tools/lldb/source/Expression/CMakeFiles/lldbExpression.dir/UserExpression.cpp.o
111.695 [1284/3/3900] Building CXX object tools/lldb/source/Commands/CMakeFiles/lldbCommands.dir/CommandObjectTarget.cpp.o
112.944 [1284/2/3901] Linking CXX shared library lib/libclang.so.21.0.0git
113.098 [1284/1/3902] Linking CXX shared library lib/libclang-cpp.so.21.0git
```
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