build(deps): bump ecdsa from 0.13.3 to 0.13.4 (#505)

Bumps [ecdsa](https://github.com/RustCrypto/signatures) from 0.13.3 to 0.13.4.
- [Release notes](https://github.com/RustCrypto/signatures/releases)
- [Commits](RustCrypto/signatures@ecdsa/v0.13.3...ecdsa/v0.13.4)

---
updated-dependencies:
- dependency-name: ecdsa
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]