Avoid adding margin to docutils container (from bootstrap container)

[jorisvandenbossche]

I know that in #323 we more or less decided against this, but I again ran into an issue where the added margin to a docutils container doesn't help (in this case a C++ API docs from doxygen / breathe).

I could also add this CSS to our custom CSS in the upstream package, but IMO this seems relatively safe to do here, since it specifically selects only those divs where there is also a docutils class (so it should normally never be a div that was created manually to work with bootstrap containers).

We can't really check this in our demo docs, since we don't have this case (but I checked this works for the arrow docs).

[jorisvandenbossche]

So we actually do have one case in our demo docs that runs into this: the jupyter-sphinx code cells and output blocks: https://pydata-sphinx-theme--474.org.readthedocs.build/en/474/demo/demo.html#html

Here, this change doesn't really improve things though .. (it looks strange without any margin). But you could also say that this is up to jupyter-sphinx, as it's their CSS that only gives the pre block 4px of padding.

[choldgraf]

Makes sense to me - for the future, these are the kinds of issues that we should think about in deciding whether we want to continue depending on Bootstrap, or instead use something like @pradyunsg's sphinx-basic-ng template to give us the structure we need.