fix(http): expose jsonpFactory for AoT compilation (#10730)

tools/public_api_guard/http/index.d.ts

@@ -108,6 +108,9 @@ export declare abstract class JSONPConnection implements Connection {
     abstract finished(data?: any): void;
 }
 
+/** @experimental */
+export declare function jsonpFactory(jsonpBackend: JSONPBackend, requestOptions: RequestOptions): Jsonp;
+
 /** @experimental */
 export declare class JsonpModule {
 }