meson: remove old socket_scm_helper rule

It was covered already in commit d3ca592 ("meson: convert check-block")

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20200828110734.1638685-9-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tests/Makefile.include

@@ -66,7 +66,6 @@ tests/migration/initrd-stress.img: tests/migration/stress$(EXESUF)
 	rmdir $(INITRD_WORK_DIR)
 
 tests/vhost-user-bridge$(EXESUF): tests/vhost-user-bridge.o $(test-util-obj-y) libvhost-user.a
-tests/qemu-iotests/socket_scm_helper$(EXESUF): tests/qemu-iotests/socket_scm_helper.o
 
 SPEED = quick