Userland: Replace most printf-style APIs with AK::Format APIs :^)

Author: https://github.com/linusg
Commit: f5c35fccca
Pull-request: https://github.com/SerenityOS/serenity/pull/7632
Reviewed-by: https://github.com/awesomekling

Userland/Utilities/base64.cpp

@@ -56,5 +56,5 @@ int main(int argc, char** argv)
     }
 
     auto encoded = encode_base64(buffer);
-    printf("%s\n", encoded.characters());
+    outln("{}", encoded);
 }