nixos/modules: remove trailing whitespace

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

nixos/modules/services/security/haveged.nix

@@ -21,11 +21,11 @@ in
         type = types.bool;
         default = false;
         description = ''
-          Whether to enable to haveged entropy daemon, which refills 
+          Whether to enable to haveged entropy daemon, which refills
           /dev/random when low.
         '';
       };
-      
+
       refill_threshold = mkOption {
         type = types.int;
         default = 1024;
@@ -34,16 +34,16 @@ in
           haveged should refill the entropy pool.
         '';
       };
-      
+
     };
-    
+
   };
-  
-  
+
+
   ###### implementation
-  
+
   config = mkIf cfg.enable {
-  
+
     systemd.services.haveged =
       { description = "Entropy Harvesting Daemon";
         unitConfig.Documentation = "man:haveged(8)";
@@ -63,5 +63,5 @@ in
       };
 
   };
-  
+
 }