Remove hardcoded preflightCommitment config

[viniciuskloppel]

Think it's safe to remove that line of code since anza-xyz/agave#483 got merged, right?

solana-web3.js/src/connection.ts

Line 6022 in 6f265af

? 'processed' // FIXME Remove when https://github.com/anza-xyz/agave/pull/483 is deployed.