Fix #1336 missing and invalid properties in rich text block elements

[seratch]

This pull request resolves #1336

Category (place an x in each of the [ ])

• [ ] bolt (Bolt for Java)
• [ ] bolt-{sub modules} (Bolt for Java - optional modules)
• [ ] slack-api-client (Slack API Clients)
• [x] slack-api-model (Slack API Data Models)
• [ ] *slack-api--kotlin-extension** (Kotlin Extensions for Slack API Clients)
• [ ] slack-app-backend (The primitive layer of Bolt for Java)

Requirements

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 74.81%. Comparing base (9976da9) to head (79fa8e2).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1337 +/- ## ============================================ + Coverage 74.77% 74.81% +0.03% - Complexity 4177 4181 +4 ============================================ Files 451 451 Lines 12930 12930 Branches 1331 1331 ============================================ + Hits 9668 9673 +5 + Misses 2487 2483 -4 + Partials 775 774 -1 ```

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