Update help_topic tests to HTML5

Problem/Motivation

Follow up from #2441373-99: Upgrade tests to HTML5 were help_topic tests were split out.

there is a problem in one case, on bad_html3 help topic error template.
Likely the parsing is different and produces a bit different error for that case, or there is an actual error to fix.

Steps to reproduce

The test fail in #97 was related to the approach change.
Basically the error strings are different on Masterminds\HTML5 parser, than in php DOM extension libxml2.
Gladly there seems to be only one actual relevant error tested from the library output, the rest are errors created on the test itself related to structure.

Proposed resolution

TBD

Remaining tasks

TBD

User interface changes

TBD

API changes

TBD

Data model changes

TBD

Release notes snippet