Remove flashes of content

[luke-quadratic]

They're subtle but wear on a user over time in terms of perceived quality and stability. Note the flashes you get any time you confirm content, focus on a cell, etc.

https://github.com/user-attachments/assets/ceee5b59-1003-4339-b182-33d1ade62311

[luke-quadratic]

Another flash happening around 0,0

https://github.com/user-attachments/assets/11bdf8df-c902-43b4-9c0b-b0783cfa986d

[luke-quadratic]

Data validation flash

Screencast from 19-09-24 05_38_05 PM IST (2).webm

[AyushAgrawal-A2]

Another flash happening around 0,0

fixed in https://github.com/quadratichq/quadratic/pull/1972

[luke-quadratic]

#1972 (all states appear good in prod)