gtkprintoperation-win32.c: Fix build

Hi,

From the commit message:

Include the needed headers so that we don't break the build with C4013 warnings, which are treated as errors if msvc_recommended_pragmas.h is found during build configuration.

Once again something slipped by CI as subprojects means that we can't force-include msvc_recommended_pragmas.h in CI to catch such things. Oh well...

With blessings, thank you!