Differences in `rel="external"` handling in some pophelps

[petecooper]

There's some discrepancy with how external links are handled in some pophelp entries. For example, allow_page_php_scripting has external link indicators:

https://github.com/textpattern/pophelp/blob/6f5bac48d3f7eed33cbb670d7a87426db203b33b/help/en_pophelp.xml#L548

…but admin_side_plugins doesn't:

https://github.com/textpattern/pophelp/blob/6f5bac48d3f7eed33cbb670d7a87426db203b33b/help/en_pophelp.xml#L526

Both pophelps are external links, both appear to use rel="external" target="_blank". I'm not sure what it is that's at play here, any ideas?

[philwareham]

Will investigate.