Fix bug where 'show more' sometimes did nothing
a3a1e2e01fa261698686fe8a1984b1dd5fc2197e added the padding
to maxTilesPx which was confusing the calculation of whether we
should be showing the 'show more' button or the 'show less' button.
Hopefully this fixes the issue without undoing fixes from
https://github.com/matrix-org/matrix-react-sdk/pull/4964 or the
above commit by adding the padding in all cased in `get padding()`.
