Prop 13: Change maximum block size from 21 MB to 1MB

## TL:DR:

• following a reported security advise it is recommended to make the maximum allowed block size of the BitCanna chain smaller
• passing this proposal lowers the maximum allowed block size from 21 MB to 1 MB
• since we use 300kB for our biggest blocks, the new maximum allowed block size still leaves a lot of room for growth

Description:

In a reported security advise (Amulet Security Advisory ASA-2023-002 and based on research from Jacob Gadikian for whom is interested) it was advised to investigate the maximum block size a chain needs.

Why are we doing this? For this we need to look at what happened elsewhere in the ecosystem. Recently we have seen spam on for example Osmosis where bots are spamming large amounts of data on chain. This causes the chain to have difficulties handling all transactions and resulting in the inability for users to use the chain (Osmosis in this case).

One counter-measure is reducing the maximum allowed size of each block. In our current settings this is limited to 21 MB, but our data shows that we are using only a fraction of that (maximum of 300kB per block).

We propose to change the maximum allowed block size to 1 MB. This is still 3 times higher than our current observed maximum, allowing for room to grow; but small enough to be prepared for on chain spam.

Find more information about parameters for blocks here: https://docs.cometbft.com/v0.34/spec/abci/apps#blockparamsmaxbytes