Fixes https://github.com/vector-im/riot-web/issues/14426
The issue only applies to lists which won't have a 'show less' button, as the lists with the button would have the button's height considered when determining visible tiles. For lists that were under that (1-4 rooms), the show more button wasn't being considered and thus leading to the padding being added rather than subtracted, causing an extra tile to render.
By ensuring we include the padding for both show more and show less, we ensure that no extra tiles get rendered and that the cutoff semantics are still present.
8e982f52ff