Dropdown rendering in github but not RTD

[danamlewis]

https://github.com/openaps/docs/pull/1551 moved some old information into a dropdown format...that is correct on github (dropdown works) but is not rendering in RTD (https://openaps.readthedocs.io/en/latest/docs/While%20You%20Wait%20For%20Gear/understanding-insulin-on-board-calculations.html).

It's matching the way it's done elsewhere, so there either is a change in how RTD is rendering it (unlikely) or there's something in this section that is breaking the formatting (more likely). I made several changes (https://github.com/openaps/docs/commit/66d9eb62db9c12243a3033c62e4bd885f315575a, https://github.com/openaps/docs/commit/bc27dea546ecb1d9172c10e629fad34388fb02e3, https://github.com/openaps/docs/commit/29338f63b5c9d4a7286be83b6e3278016d2e12bb, https://github.com/openaps/docs/commit/536a2f21cd74cf8d4d076d81decdda16c59a645f ) to try to resolve but haven't found it yet, so leaving this issue as a reminder to hunt down why it's not correct in RTD. If you spot it, please PR the fix!