[tracking] Fix configuration file.

- The sample configuration file didn't use sub-maps, but list items.

src/modules/tracking/tracking.conf

@@ -49,9 +49,9 @@
 # connection; it is a good idea to require internet in the welcome
 # module then.
 install:
-  - enabled: false
-  - default: false
-  - url:
+    enabled: false
+    default: false
+    url:
 
 # The machine area has one specific configuration key:
 #   style:  This string specifies what kind of tracking configuration
@@ -59,11 +59,11 @@ install:
 #           style, "neon", which edits two files in the installed
 #           system to enable system-tracking.
 machine:
-  - enabled: false
-  - default: false
-  - style: neon
+    enabled: false
+    default: false
+    style: neon
 
 # The user area is not yet implemented, and has no specific configuration.
 user:
-  - enabled: false
-  - default: false
+    enabled: false
+    default: false