[MAINTENANCE] Enable spark tests for docs

[Shinnnyshinshin]

Changes proposed in this pull request:

• This is a small PR in preparation for GREAT-223, which will bring Bring How to Create a Batch of Data from an In Memory Spark or Pandas Dataframe doc under test.
• This PR disables the --no-spark flag we used to have for the docusaurus tests by allowing Spark tests to use an existing helper function get_or_create_spark_session() instead of trying to load the findspark package, which was causing problems in Azure.
• Since the test script changed, I've also updated the line numbers referenced in the documentation accordingly.

Checklist

• My code follows the Great Expectations style guide
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added unit tests where applicable and made sure that new and existing tests are passing.
• I have run any local integration tests and made sure that nothing is broken.

[netlify]

✔️ Deploy Preview for niobium-lead-7998 ready!

🔨 Explore the source changes: c8aab15

🔍 Inspect the deploy log: https://app.netlify.com/sites/niobium-lead-7998/deploys/61817f8b209cc3000887bcb0

😎 Browse the preview: https://deploy-preview-3625--niobium-lead-7998.netlify.app

[github-actions]

HOWDY! This is your friendly 🤖 CHANGELOG bot 🤖

Please don't forget to add a clear and succinct description of your change under the Develop header in docs_rtd/changelog.rst, if applicable. This will help us with the release process. See the Contribution checklist in the Great Expectations documentation for the type of labels to use!

✨ Thank you! ✨

[alexsherstinsky]

LGTM