Doc: vcregress .bat commands list lacks "taptest"

Hi,

I found that "taptest" is missing in vcregress.bat command list in the
documentation when I tested psql and pgbench on Windows. I know there
is a plan to remove MSVC scripts[1], but is it worth adding one line
to the list for now?

[1] https://www.postgresql.org/message-id/flat/ZQzp_VMJcerM1Cs_%40paquier.xyz

I attached a patch for this case.

Regards,
Yugo Nagata

-- 
Yugo NAGATA <nagata@sraoss.co.jp>