Previously, the API list container (in the template of the
`<aio-api-list>` component) had three different CSS classes
(`.api-list-container`, `.docs-content`, `.l-content-small`) that were
all used for styling it. This seemed unnecessary and made it more difficult
to see what styles were applied to the container.
This commit removes the extra classes and consolidates the styles under
the `.api-list-container` class (which was the most descriptive one).
PR Close#40704