Cache configuration documentation

wasmtime-environ/tests/cache_fail_invalid_path_to_config.rs

@@ -5,6 +5,6 @@ use wasmtime_environ::cache_init;
 fn test_cache_fail_invalid_path_to_config() {
     let dir = tempfile::tempdir().expect("Can't create temporary directory");
     let config_path = dir.path().join("cache-config.toml"); // doesn't exist
-    let errors = cache_init(true, Some(&config_path), false, None);
+    let errors = cache_init(true, Some(&config_path), None);
     assert!(!errors.is_empty());
 }