Remove redirection of _IO_vfprintf

Since the commit

commit 698fb75b
Author: Zack Weinberg <zackw@panix.com>
Date:   Wed Mar 7 14:32:01 2018 -0500

    Add __v*printf_internal with flags arguments

_IO_vfprintf is gone.  This did not trigger any test case failures on
powerpc and powerpc64le, because there were no tests that covered it.
However, new test cases for nldbl versions of argp.h functions exposed
the problem.

Tested for powerpc64 and powerpc64le.