tests: remove unused qemu .args file

tests: remove unused qemu .args file

net-user-passt.args was generated early during testing of the passt
qemu commandline, when qemuxml2argvtest was using
DO_TEST("net-user-passt"). This was later changed to
DO_TEST_CAPS_LATEST(), so the file net-user-passt.x86_64-latest.args
is used instead, but the original (now unused) test file was
accidentally added to the original patch. This patch removes it.

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>