Updates actions/checkout to the latest stable version v4

[PixelPil0t1]

Updates actions/checkout to the latest stable version v4.

Changes:

Updates all instances of actions/checkout@v2 to actions/checkout@v4

Reference: Latest version confirmation: https://github.com/actions/checkout/releases/tag/v4.2.2

This update ensures we're using the most recent stable version of the GitHub checkout action across our CI/CD pipelines.