fix: relax typing on _fn_result_to_body to allow Any

[bdraco]

another cython3 fix for incorrect typing

[codecov[bot]]

Codecov Report

Patch coverage has no change and project coverage change: -0.07% :warning:

Comparison is base (c40c7bc) 82.46% compared to head (2e29bd8) 82.40%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #212 +/- ## ========================================== - Coverage 82.46% 82.40% -0.07% ========================================== Files 27 27 Lines 3171 3171 Branches 655 655 ========================================== - Hits 2615 2613 -2 - Misses 342 343 +1 - Partials 214 215 +1 ``` | [Files Changed](https://app.codecov.io/gh/Bluetooth-Devices/dbus-fast/pull/212?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bluetooth-Devices) | Coverage Δ | | |---|---|---| | [src/dbus\_fast/\_\_version\_\_.py](https://app.codecov.io/gh/Bluetooth-Devices/dbus-fast/pull/212?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bluetooth-Devices#diff-c3JjL2RidXNfZmFzdC9fX3ZlcnNpb25fXy5weQ==) | `0.00% <0.00%> (ø)` | | | [src/dbus\_fast/service.py](https://app.codecov.io/gh/Bluetooth-Devices/dbus-fast/pull/212?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bluetooth-Devices#diff-c3JjL2RidXNfZmFzdC9zZXJ2aWNlLnB5) | `88.65% <ø> (ø)` | | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/Bluetooth-Devices/dbus-fast/pull/212/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Bluetooth-Devices)

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