Fixes for web0

[UtkarshBhardwaj007]

1. Remove REMIX reference.
2. Add disclaimer about GH rate limits for DevContainer
3. Clearly mark hardhat as the recommended environment for smart contract development.
4. Remove PolkaVM from top as it is buggy and the documentation has been updated to use the EVM: update hardhat documentation for web0 hackathon polkadot-docs#1227