refactor: ensure zone.js can be built with typescript strict flag (#30993)

As part of FW-1265, the `zone.js` package is made compatible
with the TypeScript `--strict` flag. Read more about the strict flag [here](https://www.typescriptlang.org/docs/handbook/compiler-options.html)

PR Close #30993

packages/zone.js/lib/common/timers.ts

@@ -29,7 +29,7 @@ export function patchTimer(window: any, setName: string, cancelName: string, nam
 
   function scheduleTask(task: Task) {
     const data = <TimerOptions>task.data;
-    function timer() {
+    function timer(this: unknown) {
       try {
         task.invoke.apply(this, arguments);
       } finally {