Wrong path for tkt-doc.cls and tkzexample.sty

[Karl Berry]

Hi Alain - thanks for the note. 

    It would be better if the documents of tkz-doc folder should be
    here: 2021/texmf-dist/tex/latex/tkz-doc with the other tkz packages.

In that case, can you please rename couverture.tex to tkz-couverture.tex
or tkz-doc-couverture.tex? Or can that one file stay in the doc tree?

Also, "tkzexample.sty" would be better as tkz-doc-example.sty (or some
such), as well. Yours are not the only packages providing t(i)kz
examples, or that reduce "tikz" to "tkz".

Such generic names are fine in the doc tree, but in the runtime tree, we
have to be more careful. --thanks, karl.