python: remove single use of _PyVerify_fd

_PyVerify_fd disappeared from python with:

  https://hg.python.org/cpython/rev/e88e2049b793

https://bugzilla.gnome.org/show_bug.cgi?id=776815

python/types.c

@@ -31,8 +31,6 @@ libxml_PyFileGet(PyObject *f) {
     const char *mode;
 
     fd = PyObject_AsFileDescriptor(f);
-    if (!_PyVerify_fd(fd))
-        return(NULL);
     /*
      * Get the flags on the fd to understand how it was opened
      */