Update smptera-format-identifiers-rust requirement from 0.3.0 to 0.4.0

Updates the requirements on [smptera-format-identifiers-rust](https://github.com/dholroyd/smptera-format-identifiers-rust) to permit the latest version.
- [Commits](https://github.com/dholroyd/smptera-format-identifiers-rust/commits)

---
updated-dependencies:
- dependency-name: smptera-format-identifiers-rust
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.toml

@@ -14,7 +14,7 @@ edition = "2021"
 fixedbitset = "0.4.0"
 encoding = "0.2"
 log = "0.4"
-smptera-format-identifiers-rust = "0.3.0"
+smptera-format-identifiers-rust = "0.4.0"
 
 [dev-dependencies]
 assert_matches = "1.5.0"