dpinst-amd64.exe is not signed for Windows 10

dpinst-amd64.exe is not signed (or the signature has expired)

Steps to duplicate

- Windows 10
- Arduino IDE 1.8.11
- Open Boards Manager
- Install Arduino SAMD Boards version 1.8.4
- During the install you'll get an warning about unsigned drivers


Users can work around this by saying yes, but it's not OK to expect users to ignore this warning. Signed drivers are really important for avoiding malware. Arduino software installs shouldn't be encouraging people, especially beginners, to bypass security restrictions.

Suggested resolution: replace [dpinst-amd64.exe](https://github.com/arduino/ArduinoCore-samd/blob/master/drivers/dpinst-amd64.exe) with an updated version that has a valid signature.