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/StringImpl.cpp

@@ -42,7 +42,7 @@ void dump_all_stringimpls()
 {
     unsigned i = 0;
     for (auto& it : *g_all_live_stringimpls) {
-        dbgprintf("%u: \"%s\"\n", i, (*it).characters());
+        dbgln("{}: \"{}\"", i, *it);
         ++i;
     }
 }