[1.8.x] Fixed download instructions for cities shapefile

Thanks Daniel Wiesmann for spotting the issue.
Backport of 57d42aef97 from master.

docs/ref/contrib/gis/gdal.txt

@@ -34,9 +34,9 @@ The GDAL/OGR tools described here are designed to help you read in
 your geospatial data, in order for most of them to be useful you have
 to have some data to work with.  If you're starting out and don't yet
 have any data of your own to use, GeoDjango tests contain a number of
-simple data sets that you can use for testing. You can download them here:
+simple data sets that you can use for testing. You can download them here::
 
-https://github.com/django/django/raw/master/tests/gis_tests/data/cities/cities.shp
+    $ wget https://raw.githubusercontent.com/django/django/master/tests/gis_tests/data/cities/cities.{shp,prj,shx,dbf}
 
 Vector Data Source Objects
 ==========================
@@ -72,7 +72,7 @@ each feature in that layer.
    accessing the layers of data themselves, see the next section::
 
        >>> from django.contrib.gis.gdal import DataSource
-       >>> ds = DataSource(CITIES_PATH)
+       >>> ds = DataSource('/path/to/your/cities.shp')
        >>> ds.name
        '/path/to/your/cities.shp'
        >>> ds.layer_count                  # This file only contains one layer