Bump ecdsa from 0.16.6 to 0.16.8

[dependabot[bot]]

Bumps ecdsa from 0.16.6 to 0.16.8.

Commits

• a467b31 ecdsa v0.16.8 (#733)
• d7557a6 ecdsa: extract hazmat::{sign_prehashed, verify_prehashed}. (#731)
• 2c3d90e ecdsa: refactor Signature constructors and improve docs (#730)
• 5a01576 build(deps): bump serde_bytes from 0.11.9 to 0.11.11 (#729)
• 5ae0d0f build(deps): bump subtle from 2.4.1 to 2.5.0 (#726)
• e584cef build(deps): bump elliptic-curve from 0.13.4 to 0.13.5 (#719)
• 3a871f3 build(deps): bump digest from 0.10.6 to 0.10.7 (#720)
• ec0e19b build(deps): bump sha2 from 0.10.6 to 0.10.7 (#722)
• ada6d54 build(deps): bump der from 0.7.6 to 0.7.7 (#725)
• 36531d4 build(deps): bump ed25519-dalek from 2.0.0-rc.2 to 2.0.0-rc.3 (#724)
• Additional commits viewable in compare view

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