Remove unused parameter in UDP tests instantiation
Remove unused parameter in UDP tests instantiation

The variant kDualStack is never used by any test. It just duplicates
kIpv6 case. Because the parameters are now just kIpv4 and kIpv6, use
an int to encode the address family, instead of the enum.

PiperOrigin-RevId: 426224701

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor