remove resizeobserver code
remove resizeobserver code

seems to cause more harm than good in some cases and we shouldn't need
it if we get our calls to onHeightChanged in order.

matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk