google-ipmi-sys: srcrev bump b69209b498..b4e3704c17

Willy Tu (5):
      build: Update to c++20 and meson >= 0.57.0
      Add Google Copyright 2021
      test: Replace the C++ MOCK_METHOD<n> macros with the new MOCK_METHOD
      google-ipmi-sys: Refactor to use new version of OEM IPMI Handler
      google-ipmi-sys: Convert input to use std::span<const uint8_t>

Change-Id: I4a4d3416bcc48ca1e4c902969d669a1a4aca6d2f
Signed-off-by: Andrew Geissler <openbmcbump-github@yahoo.com>