Remove PYEXPAT_EXPORTS usage from PCBuild/pyexpat.vcxproj

[maxbachmann]

Looking through the history I was unable to find any revision where this actually did anything.

This should be a trivial enough change that it doesn't require a separate issue/news entry

[maxbachmann]

Possibly this stems from libexpat having an EXPAT_EXPORTS define in the past but that was already removed more than 20 years ago (libexpat/libexpat@5bdc756)

[picnixz]

cc @hartwork

[zooba]

Seems trivial to me, I don't see any uses of the variable anywhere.

[hartwork]

Throughout Expat upstream Git history, EXPAT_EXPORTS looks about as unused, I find zero code use a la "#ifdef" but only build system use:

# git log -p -G EXPAT_EXPORTS | lsdiff --strip=1 | sort -u
expat/bcb5/expat.bpr
expat/bcb5/expat.mak
expat/bcb5/expatw.bpr
expat/bcb5/expatw.mak
expat/bcb5/libexpat.bpr
expat/bcb5/libexpat.mak
expat/bcb5/libexpatw.bpr
expat/bcb5/libexpatw.mak
expat/lib/expat.dsp
expat/lib/expatw.dsp

And in CPython:

# git log -p -G PYEXPAT_EXPORTS | lsdiff --strip=1 | sort -u
PCbuild8/pyexpat/pyexpat.vcproj
PCbuild9/pyexpat.vcproj
PCbuild/pyexpat.vcproj
PCbuild/pyexpat.vcxproj
PC/VS8.0/pyexpat.vcproj
PC/VS9.0/pyexpat.vcproj

I think it's safe to remove.