Fix / prohibit the use of old ABTester versions

[valentino-amadeus]

What is the purpose of this pull request?

To prevent the user from using old versions of the ABTester.

What problem is this solving?

Some old versions of vtex.ab-tester haven't been working properly.
Also, this change will simplify the cli's code.

Types of changes

• Refactor (non-breaking change that only makes the code better)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Requires change to documentation, which has been updated accordingly.

Chores checklist

• Update CHANGELOG.md

[valentino-amadeus]

This last test keeps timing out :kaotico:

[valentino-amadeus]

Seems to be common :harold-pain: yarnpkg/yarn#8242

[valentino-amadeus]

Just tried again, and it worked! 🎉 :watt:

[gris]

Please lint your project and commit again

[gris]

Approving with the disclaimer that I didn't test the plugin nor have enough context about the removals on promptSignificanceLevel

[valentino-amadeus]

promptSignificanceLevel has only been used with old versions of vtex.ab-tester. It will not be possible to use these old versions anymore.