test(fix-doctest): fix doctests where a function is wrapped around a doctest but the function is never called

In the doctests in kem.rs, the actual tests that are run to verify that the KyberKem and the DummyKem actually work
are wrapped inside a function to make use of the ?-operator. However, these functions were never called and thus
the tests weren't really helpful and didn't provide proper coverage.

cipher-traits/Cargo.toml

@@ -14,3 +14,4 @@ readme = "readme.md"
 [dev-dependencies]
 rosenpass-oqs = { workspace = true }
 rosenpass-secret-memory = { workspace = true }
+anyhow = {workspace = true}