zehata

Fixes #3202

I wanted to refactor the style class names to use `left` or `right` instead of `preReq-` so that it is easier to understand, but that is beyond the scope of...

Re: https://github.com/nusmodifications/nusmods/pull/3840/files#diff-c16227ad8088f0a3a8edf1ae53344bb0189198cb956157ec0a9083cf3e7069f9L106-L112 The code originally had `prereqNode` class on conditional nodes. As far as I understand, modules don't conditionally unlock other modules, i.e. there are no situations like so: ```...

Update: I have a working copy of a version with a toggle in settings, but I am still refactoring. See preview at temporary branch https://github.com/zehata/nusmods/tree/zehata/website-module-page/3202/toggleable-left-to-right-prerequisites-trees-wip  

Reverted to draft because of  Update: Looks like it was already like this, just not visible when it was on the right. Fixed regardless. 

Rebased onto 0f33a55

Toggleable implementation extending this PR is at #3842. **Please note that the branch in that PR diverges from this branch and cannot both be merged.**

I found this bug report on the same issue: https://bugs.launchpad.net/ubuntu/+source/vala-panel-appmenu/+bug/2107638 Linking it for reference

Also, while doing testing, I realized that the error occurred before writing to state, so users' configs were actually not overwritten. Nonetheless, I think it would make more sense to...

Looks like it's caused by FIN2704 being an available module, which wraps it in a button that is invisible