Slot explanation paragraph sometimes gets displayed multiple times on a page

[GCHQ-Developer-847]

Summary of the bug

On pages for components which have subcomponents, the paragraph above the slots tables (explaining what slots are) gets repeated multiple times throughout the page.

🪜 How to reproduce

1. Go to the top navigation code page, for example.
2. Scroll down through the sections for the different subcomponents e.g. "Navigation item details", "Navigation button details".
3. See that the paragraph under the "Slots" headings is displayed once for each subcomponent slot table, and it is therefore repeated multiple times.

📸 Screenshots or code

This is the paragraph that is repeated:

🧐 Expected behaviour

While this is not a huge deal, it does mean that there is a lot of redundant information being displayed. It should really only be shown once per page at most.

[MI6-255]

Bigger issue here of looking at how we format the pages with sub children components