Update heck requirement from 0.4 to 0.5 (#602)

---
updated-dependencies:
- dependency-name: heck
  dependency-type: direct:production
...

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

rustler_codegen/Cargo.toml

@@ -15,7 +15,7 @@ proc_macro = true
 [dependencies]
 syn = { version = "2.0", features = ["full", "extra-traits"] }
 quote = "1.0"
-heck = "0.4"
+heck = "0.5"
 proc-macro2 = "1.0"
 
 [dev-dependencies]