Gallery Updates to include Python3 info

[QilongTang]

Please Note:

1. Before submitting the PR, please review How to Contribute to Dynamo
2. Dynamo Team will meet 1x a month to review PRs found on Github (Issues will be handled separately)
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Purpose

Declarations

Check these if you believe they are true

• The codebase is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.
• Changes to the API follow Semantic Versioning and are documented in the API Changes document.
• This PR modifies some build requirements and the readme is updated

Reviewers

FYIs

@Amoursol @DynamoDS/dynamo

[QilongTang]

Got sign off from @Amoursol , merging and will cherrypick soon

[aparajit-pratap]

@QilongTang I'm assuming you have tested the updated gallery in D4R locally?

[QilongTang]

@aparajit-pratap Yes, the attached picture in this PR is from testing