Fixed #26774 -- Corrected value of default_zoom in GeoModelAdmin doc

docs/ref/contrib/gis/admin.txt

@@ -20,7 +20,7 @@ GeoDjango's admin site
 
     .. attribute:: default_zoom
 
-    The default zoom level to use.  Defaults to 18.
+    The default zoom level to use.  Defaults to 4.
 
     .. attribute:: extra_js