Remove unused wait_event_info parameter in FileStartReadV()

Hi hackers,

While working on wait events related stuff, I noticed that the wait_event_info
parameter in FileStartReadV() is unused.

The unused parameter is there since 50cb7505b301, and I think it's ok to just
remove it (as it is set correctly in pgaio_io_perform_synchronously()).

PFA, a patch doing so.

BTW, out of curiosity I launched:

run-clang-tidy -checks="-*,misc-unused-parameters" | grep -c "warning: parameter.*is unused"
2008

That's quite a lot, but I did look at some of them randomly and they were
coming from callbacks (which can make sense). That might need a deeper analysis
though (to check if there are some outside of the callback cases).

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com