Updated an old note about GEOSGeometry.transform

.. note::

    Requires GDAL.

.. note::

   Prior to 1.3, this method would silently no-op if GDAL was not available.

   Now, a :class:`~django.contrib.gis.geos.GEOSException` is raised as

   application code relying on this behavior is in error. In addition,

   use of this method when the SRID is ``None`` or less than 0 now also generates

   a :class:`~django.contrib.gis.geos.GEOSException`.

    Requires GDAL. Raises :class:`~django.contrib.gis.geos.GEOSException` if

    GDAL is not available or if the SRID is ``None`` or less than 0.

``Point``

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