build(deps): bump spki from 0.7.2 to 0.7.3 (#762)

Bumps [spki](https://github.com/RustCrypto/formats) from 0.7.2 to 0.7.3.
- [Commits](RustCrypto/formats@spki/v0.7.2...spki/v0.7.3)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

ecdsa/Cargo.toml

@@ -25,7 +25,7 @@ digest = { version = "0.10.7", optional = true, default-features = false, featur
 rfc6979 = { version = "0.4", optional = true, path = "../rfc6979" }
 serdect = { version = "0.2", optional = true, default-features = false, features = ["alloc"] }
 sha2 = { version = "0.10", optional = true, default-features = false, features = ["oid"] }
-spki = { version = "0.7.2", optional = true, default-features = false }
+spki = { version = "0.7.3", optional = true, default-features = false }
 
 [dev-dependencies]
 elliptic-curve = { version = "0.13", default-features = false, features = ["dev"] }