Removed obsolete GEOS 3.5 requirement note.

Follow up to ea87a85fad9994dbb0748df25bc9c2d99b24809b.

docs/ref/contrib/gis/geos.txt

@@ -801,7 +801,7 @@ Geometry Collections
 
     .. attribute:: closed
 
-        Returns ``True`` if and only if all elements are closed. Requires GEOS 3.5.
+        Returns ``True`` if and only if all elements are closed.
 
 ``MultiPolygon``
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