LibWeb: Port HTMLToken::to_deprecated_string to new AK String

Author: https://github.com/shannonbooth
Commit: 1f8d72da8e
Pull-request: https://github.com/SerenityOS/serenity/pull/21815
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/HTML/Parser/HTMLToken.cpp

@@ -8,7 +8,7 @@
 
 namespace Web::HTML {
 
-DeprecatedString HTMLToken::to_deprecated_string() const
+String HTMLToken::to_string() const
 {
     StringBuilder builder;
 
@@ -70,7 +70,7 @@ DeprecatedString HTMLToken::to_deprecated_string() const
         builder.appendff("@{}:{}-{}:{}", m_start_position.line, m_start_position.column, m_end_position.line, m_end_position.column);
     }
 
-    return builder.to_deprecated_string();
+    return MUST(builder.to_string());
 }
 
 }