Address PR review feedback

Author: datibbaw

lib/ipaddr.rb

@@ -219,7 +219,6 @@ def to_hex
     when Socket::AF_INET6
       @addr.to_s(16).rjust(32, '0')
     else
-      # In case we ever add support for AF_INET8, this should raise an error.
       raise AddressFamilyError, "unsupported address family"
     end
   end

test/test_ipaddr.rb

@@ -1,11 +1,8 @@
 # frozen_string_literal: true
 require 'test/unit'
-require 'core_assertions'
 require 'ipaddr'
 
 class TC_IPAddr < Test::Unit::TestCase
-  include Test::Unit::CoreAssertions
-
   def test_s_new
     [
       ["3FFE:505:ffff::/48"],