[ref model] update serialization lib githash

This patch updates the serialization lib githash to include:

23f755a [serialization_lib] update tosa_serializer.py
30b9ca8 [serialization_lib] update README.md
199425b Set warnings as errors
a24fbe5 [serialization_lib] Add Op Info
9e3b662 Avoid supplying unsupported linker flags
877c7ff Use portable type with random engine
b22b01d Apply hardened flags to test/gtest subdir and fixed the warnings

Signed-off-by: Tai Ly <tai.ly@arm.com>
Change-Id: I15ca084c334595d42b7774c83222631b70d1e72a