remove fragile assert

The assert basically wants the following to always be true (but it aint)

floor(int + 0.5 + float) == floor(0.5 + float) + int

... where int + 0.5 happens first, and then we add the float.

BUG=skia:4825
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1609873003

Review URL: https://codereview.chromium.org/1609873003
1 file changed