remove class defining of directory from fdp-primer and advise to use filename

[jgh]

Summary

remove class defining of directory from fdp-primer and advise to use filename

[wblock]

This looks good to me. Rejoining these lines after removing the attribute still seems like a whitespace-only change on the second line. We should get input from a translator on that. Benedict, what do you think?

[bcr]

I wouldn't mind. I have to touch the line to shorten the tag anyway, so why bother? ;-)

[jgh]

If it is okay, please mark as accepted, and I will commit. Thanks for the review!