test: [ETH-811] Fix crashing Solidity compiler download

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Changes

Bumped NodeJS minor version.

Background

There has been a bugfix in the NodeJS v18.18 (nodejs/node#48435) so that it works better with the undici library (nodejs/undici#2173). That library is used by Harhat internally, e.g. when it downloads Solidity compilers.

The bug caused compiler downloads (https://github.com/NomicFoundation/hardhat/blob/40673c6ff9742898920d0e92ccd630e1a685b434/packages/hardhat-core/src/internal/util/download.ts#L23) to crash the hardhat compile task. There was no visible error message from that crash.

As the compilation terminated, the next CI phase (tsc -p tsconfig.build.json in build.sh) failed. These kind of error messages were shown:

Error: src/exports.ts(1,66): error TS2307: Cannot find module '../artifacts/contracts/OperatorTokenomics/Operator.sol/Operator.json' or its corresponding type declarations.

[linear]

ETH-811 Fix contract compilation in CI