AK: Use new format functions.

Author: https://github.com/asynts
Commit: 1d96d5eea4
Pull-request: https://github.com/SerenityOS/serenity/pull/3705
Reviewed-by: https://github.com/awesomekling

AK/URLParser.cpp

@@ -96,7 +96,7 @@ String urlencode(const StringView& input)
     for (char ch : input) {
         if (in_userinfo_set((u8)ch)) {
             builder.append('%');
-            builder.appendf("%02X", (u8)ch);
+            builder.appendff("{:02X}", ch);
         } else {
             builder.append(ch);
         }