"toctree" text appears on HTML version of the page

[mark2016]

Hi, the guide to contributing documentation appears to have a build error, I expect from a syntax error in the underlying page.

URL to the problem page is https://symfony.com/doc/current/contributing/documentation/index.html

The page appears to have rendered incorrectly, as "toctree" is an instruction to build a table of contents, should not be visible in the rendered version:

[javiereguiluz]

This hidden toctree was needed when using Sphinx as the RST parser because Sphinx requires all files to be included in some toctree. Now that we use a different, and more tolerant, RST parser I think this is no longer needed. So, I'm trying to fix this in #16632 just by removing this unneeded toctree.