PrepareProposal always passes v0 to GovSquareSizeUpperBound

[evan-forbes]

Unlike ProcessProposal, when PreparePropsoal creates a sdk context it's not setting the version in the header. This becomes an issue when callingGovMaxSquareSize, which uses the app version found in the header.

celestia-app/app/square_size.go

Line 22 in ef3c0d5

hardMax := appconsts.SquareSizeUpperBound(ctx.BlockHeader().Version.App)

When the version changes, v0 will still be used for GovMaxSquareSize. To fix this, GovSquareSizeUpperBound should always use the paramstore/baseapp app version.

[rootulp]

I'm preemptively re-opening this issue based on the revert in #3089

I think we need unit tests for square_size.go that tests the behavior of this function given different contexts (i.e. what happens if app version is 0, 1, 2. What happens when the block version is 0, 1, 2)