unit-test: Update gtest source rev to fix std::span issue

The std::span does not support some gtest MACROS and is fixed in
https://github.com/google/googletest/pull/3195 and
https://github.com/google/googletest/commit/e4717df71a4f45bf9f0ac88c6cd9846a0bc248dd

Including the fixes to support std::span in gtests.

Match the openembedded gtest version in
https://github.com/openembedded/meta-openembedded/pull/564

Change-Id: Ia0171160ee7a0a36c2fb27eb441e25cdec9ba9f1
Signed-off-by: Willy Tu <wltu@google.com>
1 file changed