nixos/smokeping: Replace the tabs in cfg.targetConfig

This was inconsistent with the rest of the module.

nixos/modules/services/networking/smokeping.nix

@@ -241,18 +241,18 @@ in
       targetConfig = mkOption {
         type = types.lines;
         default = ''
-					probe = FPing
-					menu = Top
-					title = Network Latency Grapher
-					remark = Welcome to the SmokePing website of xxx Company. \
-									 Here you will learn all about the latency of our network.
-					+ Local
-					menu = Local
-					title = Local Network
-					++ LocalMachine
-					menu = Local Machine
-					title = This host
-					host = localhost
+          probe = FPing
+          menu = Top
+          title = Network Latency Grapher
+          remark = Welcome to the SmokePing website of xxx Company. \
+                   Here you will learn all about the latency of our network.
+          + Local
+          menu = Local
+          title = Local Network
+          ++ LocalMachine
+          menu = Local Machine
+          title = This host
+          host = localhost
         '';
         description = "Target configuration";
       };