Update secret-service requirement from 3 to 4

Updates the requirements on [secret-service](https://github.com/hwchen/secret-service-rs) to permit the latest version.
- [Release notes](https://github.com/hwchen/secret-service-rs/releases)
- [Changelog](https://github.com/hwchen/secret-service-rs/blob/master/CHANGELOG.md)
- [Commits](hwchen/secret-service-rs@v3.0.0...v4.0.0)

---
updated-dependencies:
- dependency-name: secret-service
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -40,14 +40,14 @@ security-framework = { version = "2.6", optional = true }
 security-framework = { version = "2.6", optional = true }
 
 [target.'cfg(target_os = "linux")'.dependencies]
-secret-service = { version = "3", optional = true }
+secret-service = { version = "4", optional = true }
 linux-keyutils = { version = "0.2", features = ["std"], optional = true }
 
 [target.'cfg(target_os = "freebsd")'.dependencies]
-secret-service = { version = "3", optional = true }
+secret-service = { version = "4", optional = true }
 
 [target.'cfg(target_os = "openbsd")'.dependencies]
-secret-service = { version = "3", optional = true }
+secret-service = { version = "4", optional = true }
 
 [target.'cfg(target_os = "windows")'.dependencies]
 byteorder = { version = "1.2", optional = true }