test: fix typings for DoneFn (#25163)

This also fixes CI tests, which were accidentally broken in #24663.

PR Close #25163

tools/public_api_guard/core/testing.d.ts

@@ -148,7 +148,7 @@ export declare type TestModuleMetadata = {
 export declare function tick(millis?: number): void;
 
 /** @experimental */
-export declare function withBody<T>(html: string, blockFn: T): T;
+export declare function withBody<T extends Function>(html: string, blockFn: T): T;
 
 /** @experimental */
 export declare function withModule(moduleDef: TestModuleMetadata): InjectSetupWrapper;

tools/types-ext/jasminewd2.d.ts

@@ -6,6 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+/// <reference types="jasminewd2" />
+
 /**
  * Extended typings for `jasminewd2`.
  *