Update jsonwebkey requirement from 0.3 to 0.4 in /spiffe (#182)

---
updated-dependencies:
- dependency-name: jsonwebkey
  dependency-version: 0.4.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

spiffe/Cargo.toml

@@ -40,7 +40,7 @@ log = {version = "0.4", optional = true }
 hyper-util = { version = "0.1.8", default-features = false }
 
 [dev-dependencies]
-jsonwebkey = { version = "0.3", features = ["generate", "jwt-convert"] }
+jsonwebkey = { version = "0.4", features = ["generate", "jwt-convert"] }
 tokio = { version = "1", features = ["macros"] }
 once_cell = "1"