test: accept recursive annotated-allOf snapshot (Box<Expression> self-reference)

Author: lightsofapollo

src/snapshots/openapi_to_rust__test_helpers__recursive_annotated_allof.snap

@@ -0,0 +1,18 @@
+---
+source: src/test_helpers.rs
+expression: "&generated_code"
+---
+//! Generated types from OpenAPI specification
+//!
+//! This file contains all the generated types for the API.
+//! Do not edit manually - regenerate using the appropriate script.
+#![allow(clippy::large_enum_variant)]
+#![allow(clippy::format_in_format_args)]
+#![allow(clippy::let_unit_value)]
+#![allow(unreachable_patterns)]
+use serde::{Deserialize, Serialize};
+#[derive(Debug, Clone, Deserialize, Serialize, Default)]
+pub struct Expression {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub not: Option<Box<Expression>>,
+}