Bump cosmwasm rustoptimizer to 0.12.6, avoid aarch64 wasms in prod

[sascha1337]

Refs:

whoami/scripts/deploy_ci.sh

Line 18 in 22642b6

cosmwasm/rust-optimizer:0.12.5

https://github.com/CosmosContracts/juno/actions/runs/2350428096/workflow#L20

CosmWasm/optimizer@1d4bd67

• uses latest stable rust:1.60.0-alpine
• includes an important (!) warning, regarding unsafe/unpredictable implications that can occur, if aarch64 built wasm blobs are being used in production

⚠️ I highly recommend anyone to use the default Linux/amd64 docker image, to build contracts on M1 / arm64 machines. Qemu is being used automatically if needed. Ignore the docker warning inside the log. If it does not work, try the following fixes:

1. Enable Rosetta on your M1 machine
2. Increase GB ram allocation on Docker Desktop