fix: use direct download urls for win32 clients 4.0.4 and 4.0.5

[nilsding]

Workaround for nextcloud/desktop#9347, this should enable Windows clients 4.0.4 and 4.0.5 to download the update installer again.

tested locally:

• $stableVersion = '4.0.5'

  # client 4.0.3 -> github
  % curl -s '127.0.0.1:12345/client/?version=4.0.3.20260119&platform=win32&osRelease=windows&osVersion=11&kernelVersion=10.0.26200&oem=Nextcloud&buildArch=x86_64&currentArch=x86_64&versionsuffix=&channel=stable&msi=true' | xml_pp | grep downloadurl
    <downloadurl>https://github.com/nextcloud-releases/desktop/releases/download/v4.0.5/Nextcloud-4.0.5-x64.msi</downloadurl>
  
  # client 4.0.4 -> download server
  % curl -s '127.0.0.1:12345/client/?version=4.0.4.20260119&platform=win32&osRelease=windows&osVersion=11&kernelVersion=10.0.26200&oem=Nextcloud&buildArch=x86_64&currentArch=x86_64&versionsuffix=&channel=stable&msi=true' | xml_pp | grep downloadurl
    <downloadurl>https://download.nextcloud.com/desktop/releases/Windows/Nextcloud-4.0.5-x64.msi</downloadurl>
  
  # client 4.0.5 -> empty response, as the client already is on the same or newer version
  % curl -s '127.0.0.1:12345/client/?version=4.0.5.20260119&platform=win32&osRelease=windows&osVersion=11&kernelVersion=10.0.26200&oem=Nextcloud&buildArch=x86_64&currentArch=x86_64&versionsuffix=&channel=stable&msi=true' | xml_pp | grep downloadurl
  

• $stableVersion = '4.0.7'

  # client 4.0.3 -> github
  % curl -s '127.0.0.1:12345/client/?version=4.0.3.20260119&platform=win32&osRelease=windows&osVersion=11&kernelVersion=10.0.26200&oem=Nextcloud&buildArch=x86_64&currentArch=x86_64&versionsuffix=&channel=stable&msi=true' | xml_pp | grep downloadurl
    <downloadurl>https://github.com/nextcloud-releases/desktop/releases/download/v4.0.7/Nextcloud-4.0.7-x64.msi</downloadurl>
  
  # client 4.0.4 -> download server
  % curl -s '127.0.0.1:12345/client/?version=4.0.4.20260119&platform=win32&osRelease=windows&osVersion=11&kernelVersion=10.0.26200&oem=Nextcloud&buildArch=x86_64&currentArch=x86_64&versionsuffix=&channel=stable&msi=true' | xml_pp | grep downloadurl
    <downloadurl>https://download.nextcloud.com/desktop/releases/Windows/Nextcloud-4.0.7-x64.msi</downloadurl>
  
  # client 4.0.5 -> download server
  % curl -s '127.0.0.1:12345/client/?version=4.0.5.20260119&platform=win32&osRelease=windows&osVersion=11&kernelVersion=10.0.26200&oem=Nextcloud&buildArch=x86_64&currentArch=x86_64&versionsuffix=&channel=stable&msi=true' | xml_pp | grep downloadurl
    <downloadurl>https://download.nextcloud.com/desktop/releases/Windows/Nextcloud-4.0.7-x64.msi</downloadurl>
  
  # client 4.0.6 -> github
  % curl -s '127.0.0.1:12345/client/?version=4.0.6.20260119&platform=win32&osRelease=windows&osVersion=11&kernelVersion=10.0.26200&oem=Nextcloud&buildArch=x86_64&currentArch=x86_64&versionsuffix=&channel=stable&msi=true' | xml_pp | grep downloadurl
    <downloadurl>https://github.com/nextcloud-releases/desktop/releases/download/v4.0.7/Nextcloud-4.0.7-x64.msi</downloadurl>