docs: remove second "Docker image" non-example section

[MikeMcC399]

This PR removes the second section Docker image for the following reasons:

• It does not explain how to use the GitHub action. On the contrary it explains how not to use it.
• It is confusing, because there is another section higher up in the README file with exactly the same header Docker image which does explain how to use the GH Action with a Docker container.
• With the addition of documentation for pnpm in PR docs: add pnpm example #844 it would need to be explained for completeness how this could also be a solution for using a Docker image also without a pnpm-lock.yaml file.

---

Here is the text to be removed:

Docker image

If your repository does not have package.json or yarn.json (maybe it contains a static site and does not need any dependencies), you can run Cypress tests using cypress/included:... Cypress Docker images. In that case you don't even need this GH Action, instead use the Docker container and write cypress run command like this example from cypress-gh-action-included (legacy)

name: included
on: push
jobs:
  cypress-run:
    runs-on: ubuntu-22.04
    # Docker image with Cypress pre-installed
    # https://github.com/cypress-io/cypress-docker-images/tree/master/included
    container: cypress/included:3.8.3
    steps:
      - uses: actions/checkout@v3
      - run: cypress run

[github-actions]

🎉 This PR is included in version 5.6.0 🎉

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