size: Default to '--sort=self'.

* guix/scripts/size.scm (%default-options): Change default value for
'profile<?.
* doc/guix.texi (Invoking guix size): Adjust accordingly.

doc/guix.texi

@@ -6383,10 +6383,10 @@ Use substitute information from @var{urls}.
 Sort lines according to @var{key}, one of the following options:
 
 @table @code
-@item closure
-the total size of the item's closure (the default);
 @item self
-the size of each item.
+the size of each item (the default);
+@item closure
+the total size of the item's closure.
 @end table
 
 @item --map-file=@var{file}

guix/scripts/size.scm

@@ -282,7 +282,7 @@ Report the size of PACKAGE and its dependencies.\n"))
 
 (define %default-options
   `((system . ,(%current-system))
-    (profile<? . ,profile-closure<?)))
+    (profile<? . ,profile-self<?)))
 
 
 ;;;