nixos/modules: remove trailing whitespace

This leads to ci failure otherwise if the file gets changed.
git-blame can ignore whitespace changes.

nixos/modules/virtualisation/azure-image.nix

@@ -6,7 +6,7 @@ let
 in
 {
   imports = [ ./azure-common.nix ];
-  
+
   options = {
     virtualisation.azureImage.diskSize = mkOption {
       type = with types; int;