SSCCE CI pipeline broken after dropping support for Node 14

[Hornwitser]

Issue Creation Checklist

• I understand that my issue will be automatically closed if I don't fill in the requested information
• I have read the contribution guidelines

Bug Description

After #16058 code which uses Node.js features that are supported in Node.js v16, but not v14 have made its way into the code base, but the CI pipeline for the SSCCE repository which people are instructed to use to demonstrate problems in Sequelize have not been updated to reflect this. Consequently it fails to run.

Reproducible Example

Here is the link to the SSCCE for this issue: sequelize/sequelize-sscce#260

What do you expect to happen?

SSCCE CI Pipeline should work with Sequelize v7.

What is actually happening?

Tests throw an error before user code is even run:

An unhandled rejection occurred:
/home/runner/work/sequelize-sscce/sequelize-sscce/node_modules/@sequelize/core/lib/associations/belongs-to.js:140
      newForeignKeyAttribute.onDelete ??= newForeignKeyAttribute.allowNull !== false ? "SET NULL" : "CASCADE";
                                      ^^^

SyntaxError: Unexpected token '??='

Environment

• Sequelize version: v7.0.0-alpha.27
• Node.js version: 14.21.3 (CI pipeline tries to run with an unsupported version)
• If TypeScript related: TypeScript version: n/a
• Database & Version: all dialects
• Connector library & Version: n/a

Would you be willing to resolve this issue by submitting a Pull Request?

• Yes, I have the time and I know how to start.
• Yes, I have the time but I will need guidance.
• No, I don't have the time, but my company or I are supporting Sequelize through donations on OpenCollective.
• No, I don't have the time, and I understand that I will need to wait until someone from the community or maintainers is interested in resolving my issue.

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[Hornwitser]

I guess my help is not needed here.