fix(locale-search): fix class fields error for inputTimeout (#12112)

### Related Ticket(s)

Closes #12087 (partially, see also #12088)

### Description

Fixes the following error reported when using react  wrapped components:

```
Error: The following properties on element c4d-locale-search will not trigger updates as expected because they are set using class fields: inputTimeout. Native class fields and some compiled output will overwrite accessors used for detecting changes. See https://lit.dev/msg/class-field-shadowing for more information.
```

### Changelog

**Changed**

- Declare `inputTimeout` class property of `ThrottledInputMixin` as abstract, relying on children to implement.

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packages/web-components/src/globals/mixins/throttled-input.ts

@@ -72,7 +72,7 @@ const ThrottledInputMixin = <T extends Constructor<HTMLElement>>(Base: T) => {
     /**
      * The throttle timeout to run query upon user input.
      */
-    inputTimeout = 200;
+    abstract inputTimeout: number;
 
     connectedCallback() {
       // TS seems to miss `HTMLElement.prototype.connectedCallback()` definition