update mocha to fix mochajs/mocha#3090 (see: 1808c5b)

Author: trajan0x

hardhat.config.ts

@@ -104,7 +104,8 @@ let config: HardhatUserConfig = {
     target: "ethers-v5",
   },
   dodoc: {
-    runOnCompile: true,
+    // skip doc generation on ci
+    runOnCompile: process.env.CI == "",
     debugMode: false,
     // pre solidity 5 breaks docgen
     exclude: ["MultisigWallet", "WETH9"]