refactor(common): remove unnecesary null (#47238)

These null values are unused and unecessary. I suspect it's a remnant from when the codebase was transpiled to Dart.

PR Close #47238

packages/common/testing/src/mock_platform_location.ts

@@ -240,5 +240,5 @@ export class MockPlatformLocation implements PlatformLocation {
 }
 
 export function scheduleMicroTask(cb: () => any) {
-  Promise.resolve(null).then(cb);
+  Promise.resolve().then(cb);
 }