resolv: Remove bogus targets that build ga_test

Remove the bogus targets (and source) that supposedly build ga_test.
This code was added to resolv very early in the development process
but does not appear to be an actual test program. The target for
building this file is tests but because the glibc Make system is
built the way it is, the target is overriden by higher-level tests
targets and, therefore, the ga_test program is never built. Removing
the target and the source code makes the resolv/Makefile less confusing.

Tested by building and running 'make check' on 64 bit host running
Kernel 4.10.0-19 configured with
 --prefix=/home/hawkinsw/code/glibc-build/install
 --enable-hardcoded-path-in-tests
 --disable-mathvec

Reviewed-by: Carlos O'Donell <carlos@redhat.com>