selftests: bonding: remove redundant delete action of device link1_1

When run command "ip netns delete client", device link1_1 has been
deleted. So, it is no need to delete link1_1 again. Remove it.

Signed-off-by: Zhengchao Shao <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

tools/testing/selftests/drivers/net/bonding/bond-arp-interval-causes-panic.sh

···
 {
 	ip netns delete server || true
 	ip netns delete client || true
-	ip link del link1_1 || true
 }
 
 trap finish EXIT