Note on change emergency key to nothing-in-my-sleeve

docs/develop/smart-contracts/governance.md

@@ -65,4 +65,5 @@ Validators indeed voted to assign that key to TON Foundation in July 2021 (maste
 History of emergency updates:
  - On April 17, 2022, the number of applications for the election grew big enough that the election could not be conducted under gas limits at that moment. In particular, elections required more than 10 million of gas, while the block `soft_limit` and `hard_limit` were set to `10m` and `20m`  (ConfigParam 22), `special_gas_limit` and `block_gas_limit` were set to `10m` and `10m`, respectively (ConfigParam 20). That way, new validators cannot be set, and due to reaching the block gas limit, transactions that process internal messages on the masterchain could not be included in the block. In turn, that leads to the inability to vote for configuration updates (it was impossible to win the required number of rounds since the current round was unable to finish). An emergency key was used to update ConfigParam 22 `soft_limit` to 22m and `hard_limit` to 25m (in block `19880281`) and ConfigParam 20 `special_gas_limit` to 20m and `block_gas_limit` to 22m (in block `19880300`). As a result, the election was successfully conducted, the next block consumed `10 001 444` gas. The total postponement of elections was about 6 hours, and the functionality of the base chain was unaffected.
  - On March 2, 2023, the number of applications for the election grew big enough that even `20m` were not enough to conduct election. However, this time masterchain continue to process external messages due to higher `hard_limit`. An emergency key was used to update ConfigParam 20 `special_gas_limit` to 25m and `block_gas_limit` to 27m (in block `27747086`). As a result, the election was successfully conducted in next block. The total postponement of elections was about 6 hours, besides elections, functionality of the both master chain and base chain was unaffected.
- - On November 22, 2023, key was used to [renounce itself](https://t.me/tonblockchain/221) (in block `34312810`). As a result, the only way to update network configuration parameters is through validator consensus.
+ - On November 22, 2023, key was used to [renounce itself](https://t.me/tonblockchain/221) (in block `34312810`). As a result, public key was replaced with 32 zero bytes.
+ - Due to switch to OpenSSL implementation of Ed25519 signature verification, check for special case [all bytes of public key are the same](https://github.com/ton-blockchain/ton/blob/7fcf26771748338038aec4e9ec543dc69afeb1fa/crypto/ellcurve/Ed25519.cpp#L57C1-L57C1) was disabled. As a result, check agaisnt zero public key stopped work as intended. Using this issue, emergency key was [updated on December 9](https://t.me/tonstatus/80) yet another time (in block `34665437`, [tx](https://tonscan.org/tx/MU%2FNmSFkC0pJiCi730Fmt6PszBooRZkzgiQMv0sExfY=)) to nothing-in-my-sleeve byte-sequence `82b17caadb303d53c3286c06a6e1affc517d1bc1d3ef2e4489d18b873f5d7cd1` that is `sha256("Not a valid curve point")`. Now, the only way to update network configuration parameters is through validator consensus.