Processing of <attRef> pointing at a class produces ugly output

[martindholmes]

@sydb and @martindholmes found that the output shown on this page:

https://teijenkins.hcmc.uvic.ca/job/TEIP5-dev/lastSuccessfulBuild/artifact/P5/release/doc/tei-p5-doc/en/html/ref-att.entryLike.html

is the result of the processing of a workaround for the bug in #370. However, it includes an unnecessary introductory word "Attributes". Although in this case it's a workaround, legitimate cases for using attRef then overriding it obviously exist, so this should work and should produce cleaner output.