[cairo] pycairo: set_pattern currently disabled

[Carl Worth]

As I was recently updating the pycairo bindings I noticed that the
binding for cairo_set_pattern had not been updated since the change from
accepting a cairo_surface_t* to a cairo_pattern_t*.

I imagine it would be an easy fix for someone familiar with making
python bindings to a C library.

I'm not such a person, so I've disabled the broken function for now.

-Carl