[phb:security] Fix vuln.xml testing procedure

[fernape]

Summary

In r562203 and r562204 the vuln.xml file was splitted by year.

As stated in the commit message, pkg(8) audit does not support entities and hence,
we need to use the vuln-flat.xml file to test changes to the port.

Test Plan

• Try something like this:

$ pkg audit -f ./vuln.xml gitea-1.13.4
pkg: Syntax error while parsing vulnxml
pkg: cannot process vulnxml

and then:

$ pkg audit -f ./vuln-flat.xml gitea-1.13.4
0 problem(s) in 0 installed package(s) found.

After the patch:

• igor clean
• The documentation is rendered properly.

[gbe]

Should be fine. I haven't checked the rendered output, but I am sure you did.

[fernape]

In D29219#654173, @gbe wrote:

Should be fine. I haven't checked the rendered output, but I am sure you did.

That is the rendered output. Note that there is some kind of missing icon or something. It is not related to my changes. Doing a clean clone from the repo and building the doc has that effect too.