BUG: Heading numbering is inconsistent

[bsipocz]

The heading numbering is inconsistent at the moment.

Jessica already pointed this out for the first round of review:

For the forced photometry rendered notebook, the section heading doesn't appear to have worked for section 2. I think "Use fornax cloud access API..." should be 2.1, etc. Sorry if this is a problem with the original notebook, and leet me know if you want me to change anything in the .md file

However, unfortunately, doing the heading numbering automatically does not work with the rendering, there are long open feature requests for this in the various packages we use under the hood, see executablebooks/MyST-NB#317 and references therein.

So at the moment all of the numbers should come from hand-written into heading titles.

(and IMO those will look quite ugly in jupyerlab when working with the notebooks as automated numbering works there.)

So, we either fix the manual numbering everywhere, or remove the currently added numbers. I would lean for the latter, as in the rendered version the right hand side TOC I think works nice without the numbers, but we can also add the number if you would like that.