test: pend the LIBXML_LOADED_VERSION test on freebsd

Related to #2506

test/test_version.rb

@@ -60,7 +60,13 @@ def test_version_info_for_libxml
     major = Regexp.last_match(1).to_i
     minor = Regexp.last_match(2).to_i
     bug = Regexp.last_match(3).to_i
-    assert_equal("#{major}.#{minor}.#{bug}", Nokogiri::VERSION_INFO["libxml"]["loaded"])
+    if RbConfig::CONFIG["target_os"].include?("freebsd13") && Nokogiri::VersionInfo.instance.libxml2_using_system?
+      pending("https://github.com/sparklemotion/nokogiri/issues/2506") do
+        assert_equal("#{major}.#{minor}.#{bug}", Nokogiri::VERSION_INFO["libxml"]["loaded"])
+      end
+    else
+      assert_equal("#{major}.#{minor}.#{bug}", Nokogiri::VERSION_INFO["libxml"]["loaded"])
+    end
 
     assert(version_info["libxml"].key?("iconv_enabled"))
     assert(version_info["libxslt"].key?("datetime_enabled"))