Use Prettier for JS files (#3913)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>

test/helpers/chainid.js

@@ -1,6 +1,6 @@
 const hre = require('hardhat');
 
-async function getChainId () {
+async function getChainId() {
   const chainIdHex = await hre.network.provider.send('eth_chainId', []);
   return new hre.web3.utils.BN(chainIdHex, 'hex');
 }