`SerializerRoundTrip.DeepFullTree` gtest is failing with MSVC 2026

[chyunsu3]

[ RUN      ] SerializerRoundTrip.DeepFullTree
unknown file: error: C++ exception with description "[08:58:25] D:\a\treelite\treelite\src\model_builder\model_builder.cc:126: Node with key 2 not found" thrown in the test body.

https://github.com/dmlc/treelite/actions/runs/28227735573/job/83623709179?pr=665