Exclude polyfill for WHATWG URL constructor undefined base issue

Although this polyfill is required for bug-free `new URL('http://x', undefined)` in Safari versions < 14 with an `undefined` base, we don’t use it:

```
The corejs3 polyfill added the following polyfills:
  web.url { "chrome":"61", "edge":"16", "ios":"10.3", "opera":"48", "safari":"10.1", "samsung":"8.2" }
  web.url-search-params { "chrome":"61", "edge":"16", "ios":"10.3", "opera":"48", "safari":"10.1", "samsung":"8.2" }
```

packages/govuk-frontend/babel.config.js

@@ -51,7 +51,13 @@ module.exports = function (api) {
           exclude: [
             // ES2022 Error cause is unused
             // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/cause
-            'es.error.cause'
+            'es.error.cause',
+
+            // WHATWG URL constructor `undefined` base fix is unnecessary
+            // https://bugs.webkit.org/show_bug.cgi?id=216841
+            // https://github.com/zloirock/core-js/commit/0ef4be7352e900dfa6f1eda27de22f7974576531
+            'web.url',
+            'web.url-search-params'
           ],
 
           // Replace unsupported code with polyfills