Removed unused **kwargs from GEOSFuncFactory.__call__().

[sir-sigurd]

This slightly improves performance:

Before:

$ python -m pyperf timeit -s 'from django.contrib.gis.geos import Point; p = Point()' "p.empty"  --duplicate=100
.....................
Mean +- std dev: 2.00 us +- 0.04 us

After:

$ python -m pyperf timeit -s 'from django.contrib.gis.geos import Point; p = Point()' "p.empty"  --duplicate=100
.....................
Mean +- std dev: 1.94 us +- 0.03 us