Follow up to T6769: Kleopatra: Change warning on keyserver upload

When you upload a certificate to a keyserver you get the success message "OpenPGP certificates exported successfully."
This is confusing. Additionally, the titel of the window shows the first part of nearly the same text and is cut short as that is too long:

For the window title that should be either the default window title or something short like "Success".

For the message "Upload successful." or even better "OpenPGP certificates uploaded successfully to %1" which could be either keyserver vs internal directory or the URL.
Edit 2025-05-13: We decided to keep it as simple as possible.