HeighByRows is off by one pixel

[javier-godoy]

Integration test testOpenWithItemsDefaultSize (http://127.0.0.1:8080/it/height-by-rows/10) fails in Vaadin 23.3.15 / 24.1.1 because it expects the offsetSize to be 453px but it is computed as 452px.

The test is correct: the offset size must be the same as in testOpenWithItemsFullSize (http://127.0.0.1:8080/it/height-by-rows/10;fullsize), which computes the height as 453px.