(maint) Update tests for CentOS Stream 8

ip6tables has altered its behaviour on CentOS Stream 8 so that if string_to is passed as 65535 it is considered a default value and is not shown.

Author: david22swan

spec/acceptance/firewall_attributes_ipv6_happy_path_spec.rb

@@ -268,7 +268,7 @@ class { '::firewall': }
           proto       => 'tcp',
           string_hex  => '|f4 6d 04 25 b2 02 00 0a|',
           string_algo => 'kmp',
-          string_to   => 65535,
+          string_to   => 65534,
           jump        => accept,
           protocol    => 'ip6tables',
         }
@@ -278,7 +278,7 @@ class { '::firewall': }
           dport       => '53',
           string_hex  => '! |0000ff0001|',
           string_algo => 'bm',
-          string_to   => 65535,
+          string_to   => 65534,
           jump        => 'accept',
           protocol    => 'ip6tables',
         }