AK+Everywhere: Rename String to DeprecatedString

We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)

Userland/Libraries/LibWeb/HTML/NavigationParams.h

@@ -20,7 +20,7 @@ namespace Web::HTML {
 // https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigation-params
 struct NavigationParams {
     // a navigation id
-    String id;
+    DeprecatedString id;
 
     // null or a request that started the navigation
     JS::GCPtr<Fetch::Infrastructure::Request> request;