Remove seemingly unneeded include directory in MSVC scripts
This appears to have been added way back in
ee3b4188a but it's a little
unclear why the change made in that commit is even needed given that
320c7eb8c, dated 18 months earlier, added code to copy fmgroids.h to
src/include/utils.
amcheck seems to get away without adding the additional include directory,
so perhaps dblink can get away with it too.
This builds ok in my VS2017 environment, but the buildfarm may serve as a
reminder about why
ee3b4188a was required. There's only one way to find
out for sure.
Discussion: https://postgr.es/m/CAApHDvpo6g5csCTjc_0C7DMvgFPomVb0Rh-AcW5afd=Ya=LRuw@mail.gmail.com