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/extra/jsonp.ts

@@ -42,7 +42,7 @@ Zone.__load_patch('jsonp', (global: any, Zone: ZoneType, api: _ZonePrivate) => {
           configurable: true,
           enumerable: true,
           get: function() {
-            return function() {
+            return function(this: unknown) {
               const task = global[api.symbol('jsonpTask')];
               const target = this ? this : global;
               const delegate = global[api.symbol(`jsonp${methodName}callback`)];