46f76ca8b8
Texinfo-6.8 (that was used to build the docs of nano-5.9) changed the way the @contents command is processed for HTML output, with as result a detailed table of contents at the start of the HTML page. That is ugly and too much detail. To avoid that, produce a table of contents only when generating output meant for printing. This fixes https://savannah.gnu.org/bugs/?61344. Bug existed since version 5.9.