chore: Remove deprecated region tag

[glasnt]

Description

Complements #6495

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.6 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• Please merge this PR for me once it is approved.
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample

[snippet-bot]

Here is the summary of changes.

You are about to delete 3 region tags.

• appengine/flexible/django_cloudsql/mysite/settings.py:168, tag gaeflex_py_django_staticconfig
• kubernetes_engine/django_tutorial/mysite/settings.py:111, tag gke_django_staticconfig
• run/django/mysite/settings.py:160, tag cloudrun_django_staticconfig

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