Do not allow using Infection with Codeception < 3.1.1

[maks-rafalko]

This one and ready to go.

When Test Framework adapters will be extracted to own composer packages, this will be just in infection/codeception-adapter's composer.json:

{
    "conflicts": {
        "codeception/codeception": "<3.1.1"
    }
}

Now, we can't do it in the root's composer.json, because one can use Infection with e.g. PHPSpec while having Codeception installed as well.

[tests-checker]

Thank you for contributing to Infection. We noticed you didn't add any tests. Could you please add them to make sure everything works as expected?

[maks-rafalko]

Thank you @sidz