docs(gae): Update README.md in ndb/redis_cache/ to a current Python 3 sample

[eapl-gemugami]

Description

Fixes Internal: b/389957560

Follow-up of #13054

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Lint pass: nox -s lint (see Test Environment Setup)
• Please merge this PR for me once it is approved

[ghost]

Hi team,

I'm currently reviewing this pull request and will provide my feedback shortly. In the meantime, here's a summary for you and other reviewers to quickly get up to speed:

This pull request updates the README.md file in the ndb/redis_cache/ directory to reflect a current Python 3 sample. Specifically, it addresses internal issue b/389957560 and is a follow-up to #13054.

Here's a breakdown of the changes:

• File Changed: appengine/standard/migration/ndb/redis_cache/README.md
• Changes: The README was updated to remove instructions for deploying with Python 2.7. The deployment instructions now only refer to Python 3.8 and using app3.yaml.
  • Lines 23-31 (old) were replaced with lines 23-27 (new). The old instructions for Python 2.7 deployment were removed, and the Python 3.7 deployment instruction was updated to Python 3.8.

The author has indicated that all relevant checklists have been completed, including linting and adherence to the sample guidelines.

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A little haiku to lighten the mood:

Code flows like a stream,
Fixes merge, a gentle hum,
Progress finds its way.

[ghost]

The README update looks good. Removing the Python 2.7 instructions is the right move, and updating the Python 3 instructions is helpful. Specifying Python 3.8 is also a good idea, as that is the most common Python 3 runtime used in App Engine Standard.