Update Blake dependency

[iquerejeta]

This PR simply updates the Blake2 dependency. We use the new, more flexible design, of version 0.10.4 to use an output of 32 bytes instead of 64 bytes, making merkle paths half the size.

[github-actions[bot]]

Unit Test Results

    7 files  ±0    22 suites  ±0   2m 6s :stopwatch: +40s 293 tests ±0  293 :heavy_check_mark: ±0  0 :zzz: ±0  0 :x: ±0  294 runs  ±0  294 :heavy_check_mark: ±0  0 :zzz: ±0  0 :x: ±0 

Results for commit bff8f8d9. ± Comparison against base commit 74e37fa6.

This pull request removes 1 and adds 1 tests. Note that renamed tests count towards both.

src/stm.rs - stm::StmSigner<D> ‑ new_epoch (line 404)

src/stm.rs - stm::StmSigner<D> ‑ new_epoch (line 405)