meson: fix generic location of vss headers

This is a left-over, despite requesting the change before the merge.

Fixes: commit 8821a38 ("configure, meson: replace VSS SDK checks and options with --enable-vss-sdk")
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20220222194008.610377-2-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

meson.build

@@ -1936,7 +1936,7 @@ have_vss = false
 if targetos == 'windows' and link_language == 'cpp'
   have_vss = cxx.compiles('''
     #define __MIDL_user_allocate_free_DEFINED__
-    #include <inc/win2003/vss.h>
+    #include <vss.h>
     int main(void) { return VSS_CTX_BACKUP; }''')
 endif