Put HashSet in partial-eval, was accidentally removed in last commit

Author: MarcBridner

cedar-policy/src/ffi/is_authorized.rs

@@ -26,7 +26,9 @@ use crate::{Authorizer, Decision, PolicyId, Request};
 use cedar_policy_core::validator::cedar_schema::SchemaWarning;
 use serde::{Deserialize, Serialize};
 use serde_with::serde_as;
-use std::collections::{HashMap, HashSet};
+use std::collections::HashMap;
+#[cfg(feature = "partial-eval")]
+use std::collections::HashSet;
 #[cfg(feature = "wasm")]
 use wasm_bindgen::prelude::wasm_bindgen;