Update p2panda-rs to `v0.8.1`

[adzialocha]

📋 Checklist

• [x] Add tests that cover your changes
• [x] Add this PR to the Unreleased section in CHANGELOG.md
• [x] Link this PR to any issues it closes
• [x] New files contain a SPDX license header

[codecov[bot]]

Codecov Report

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

Comparison is base (8e21b6a) 92.31% compared to head (bbf83ed) 92.30%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #599 +/- ## ========================================== - Coverage 92.31% 92.30% -0.01% ========================================== Files 109 109 Lines 18662 18662 ========================================== - Hits 17227 17226 -1 - Misses 1435 1436 +1 ```

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