[1.3.X] Fixed #16232 -- Corrected typo in geographic admin reference.…

… Thanks, Issac Kelly.

Backport of r16484 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.3.X@16486 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/ref/contrib/gis/admin.txt

@@ -50,7 +50,7 @@ GeoDjango's admin site
 
    .. attribute:: modifiable
 
-   Defaults to ``False``.  When set to ``True``, disables editing of
+   Defaults to ``True``.  When set to ``False``, disables editing of
    existing geometry fields in the admin.
 
    .. note::