That's a system prompt that the installer has no control over. It however can be easily suppressed.
I am attaching our certificate, with which you will just need to launch the following command before installing the software itself:
certutil -addstore "TrustedPublisher" sp.cer
This will add the certificate to the list of trusted publishers and the system won't pop that confirmation during the software's installation.
I also have updated the installation package to do it automatically, so alternatively you can download a fresh build from the home page.
It now should suppress any prompts during a silent installation.