ecdsa: bump elliptic-curve to v0.9.10; use ScalarBytes

[tarcieri]

Bumps the elliptic-curve crate dependency to v0.9.10, and uses the newly added ScalarBytes type to impl TryFrom<&[u8]> for Signature<C>

[codecov-commenter]

Codecov Report

Merging #284 (83ec79a) into master (f1f0e57) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 83ec79a differs from pull request most recent head 304b72f. Consider uploading reports for the commit 304b72f to get more accurate results

@@           Coverage Diff           @@
##           master     #284   +/-   ##
=======================================
  Coverage   55.29%   55.29%           
=======================================
  Files           9        9           
  Lines         293      293           
=======================================
  Hits          162      162           
  Misses        131      131           

Impacted Files	Coverage Δ
ecdsa/src/lib.rs	44.00% <100.00%> (ø)

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