msgpack and cython updates (1.2-maint)

[codecov-commenter]

Codecov Report

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

Project coverage is 82.57%. Comparing base (fe8d11c) to head (a6b66fc).

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## 1.2-maint #8134 +/- ## ============================================= + Coverage 82.56% 82.57% +0.01% ============================================= Files 38 38 Lines 10792 10792 Branches 2065 2065 ============================================= + Hits 8910 8912 +2 + Misses 1332 1331 -1 + Partials 550 549 -1 ```

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