cognitive_planning update to python3.x

[moneypi]

Description

:memo: Please include a summary of the change. I get some error when I run cognitive_planning in Python3.8, so I try to fix these errors. But I can't download AVD_Minimal.zip(https://storage.googleapis.com/active-vision-dataset/AVD_Minimal.zip) ......

Type of change

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• [x] Bug fix (non-breaking change which fixes an issue)
• [x] Documentation update
• [ ] TensorFlow 2 migration
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] A new research paper code implementation
• [ ] Other (Specify)

Tests

:memo: Please describe the tests that you ran to verify your changes.

• Provide instructions so we can reproduce.
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Test Configuration:

Checklist

• [x] I have signed the Contributor License Agreement.
• [x] I have read guidelines for pull request.
• [x] My code follows the coding guidelines.
• [x] I have performed a self code review of my own code.
• [ ] I have commented my code, particularly in hard-to-understand areas.
• [x] I have made corresponding changes to the documentation.
• [x] My changes generate no new warnings.
• [ ] I have added tests that prove my fix is effective or that my feature works.

[jaeyounkim]

@arsalan-mousavian Can you review this PR?

[jaeyounkim]

@moneypi This model is not maintained anymore, and Arsalan Mousavian(@arsalan-mousavian) has not responded yet. This model will be achieved at the end of October unless Arsalan can help.