Remove wrong and unnecessary check for setDnsForwarders

inet_pton could not parse link local address with zone id.
Additionally, setDnsForwarders has already used getaddrinfo for address parsing.

Bug: 129474773
Test: built, flashed, booted
      system/netd/tests/runtests.sh passes

Change-Id: Iea8ccd234e81ff6ddd863d920033559d436bf0d0