Remove usage of BroadcastModeBlock

[evan-forbes]

    [question] should this be `flags.BroadcastMode` per https://github.com/cosmos/cosmos-sdk/blob/7781cdb3d20bc7ebac017452897ce1e6ab3903ef/client/flags/flags.go#L114

// should be submitted async, sync, or block (see flags.BroadcastMode). If

Note: block mode was removed in cosmos/cosmos-sdk#12659. Since celestia-app currently uses cosmos-sdk v0.46.0 we can still use block here but note to future selves that we'll need to remove it when we upgrade cosmos-sdk to a release with that change

Originally posted by @rootulp in #866 (comment)

blocking until a tx is included in a block is useful for testing purposes. Since its being deprecated, we need to create a replacement and use it across the repo

[rach-id]

The QGB also rely on it to wait for signatures to be included in blocks. We will need to update that also

Edit: no longer relevant with new design