Bump post-rs to v0.6.1

[poszu]

There are a few breaking changes in the C FFI of post-rs library:

• post config is now split into ProofConfig and InitConfig,
• scrypt is now configured with N, R, and P instead of the factors for a better UX.

[codecov[bot]]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (35d0654) 70.1% compared to head (b4b08ae) 70.9%.

Files	Patch %	Lines
verifying/verifying_options.go	83.3%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #249 +/- ## ========================================= + Coverage 70.1% 70.9% +0.8% ========================================= Files 28 28 Lines 1820 1803 -17 ========================================= + Hits 1277 1280 +3 + Misses 401 385 -16 + Partials 142 138 -4 ```

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[fasmat]

We probably need to remove the custom SDKROOT on macOS M1 builds to get it working on mac. Windows and Linux seem to be good with this change and https://github.com/spacemeshos/post-rs/pull/155