selftests: fib_rule_tests: fix local IPv4 address typo

The IPv4 testing address are all in 192.51.100.0 subnet. It doesn't make
sense to set a 198.51.100.1 local address. Should be a typo.

Fixes: 65b2b493 ("selftests: net: initial fib rule tests")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>