The `getSpanRectFromText` helper function returns the location as float
values. This could be desirable in cases where the exact values matter
(for example during comparisons), but in the text layer tests we don't
need this precision. Moreover, the Puppeteer `page.mouse.move` API
apparently doesn't work correctly if float values are given as input.
Note that this test only failed because it couldn't move to the initial
selection position; any subsequent moves actually worked because the
`moveInSteps` helper function already rounded all values correctly.
This commit fixes the issue by consistently rounding all values that we
pass to Puppeteer's `page.mouse.move` API.
24b8393bfe