selftests: forwarding: fix missing backslash

Fix missing backslash, introduced in f62c5acc80.  Causes all tests to
not be installed.

Fixes: f62c5acc80 ("selftests/net/forwarding: add missing tests to Makefile")
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
Acked-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20220518151630.2747773-1-troglobit@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/forwarding/Makefile

@@ -86,7 +86,7 @@ TEST_PROGS = bridge_igmp.sh \
 	vxlan_bridge_1d_port_8472.sh \
 	vxlan_bridge_1d.sh \
 	vxlan_bridge_1q_ipv6.sh \
-	vxlan_bridge_1q_port_8472_ipv6.sh
+	vxlan_bridge_1q_port_8472_ipv6.sh \
 	vxlan_bridge_1q_port_8472.sh \
 	vxlan_bridge_1q.sh \
 	vxlan_symmetric_ipv6.sh \