Update mcr.microsoft.com/windows Docker tag to v1903

Update mcr.microsoft.com/windows from 1809 to 1903

Change-type: patch

Author: balena-renovate[bot]

Dockerfile

@@ -1,7 +1,7 @@
 # The Windows 10 base image, compatible with Windows Server 2019
 # We can't use Server Core as we need full GUI capabilities.
 # See https://hub.docker.com/_/microsoft-windows
-FROM mcr.microsoft.com/windows:1809-amd64
+FROM mcr.microsoft.com/windows:1903-amd64
 
 #################################################
 # Chocolatey