[codex] Update mdbx-containers submodule

[NewYaroslav]

Summary

• update external/mdbx-containers from c630d3e to e9e9f2f
• brings upstream CMake parent-target consumption improvements
• brings upstream non-reserved header guard cleanup and AI-agent guard rule

Upstream commits

• 560a8fc build: reuse parent-provided mdbx targets
• e9e9f2f fix: use non-reserved include guards

Checks

• cmake -S . -B build-codex-mdbx-update -G "MinGW Makefiles" -DOPTIONX_BUILD_DEPS=ON -DOPTIONX_BUILD_TESTS=ON
• cmake --build build-codex-mdbx-update --target trade_record_db_test -- -j1
• build-codex-mdbx-update/trade_record_db_test.exe --gtest_brief=1
• git diff --check