lib: Don't take a reference to the surface in get_cairo_surface()
lib: Don't take a reference to the surface in get_cairo_surface()

We don't need to keep a reference to the surface, the cairo context will
keep a reference to it until we destroy it.

Signed-off-by: Damien Lespiau <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>

dlespiau/checkmate-test-igt,yipdw/intel-gpu-tools,yipdw/intel-gpu-tools,erikarn/intel-gpu-tools,chenxianqin/intel-gpu-tools,dlespiau/checkmate-test-igt,mv0/intel-gpu-tools,dlespiau/checkmate-test-igt,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,erikarn/intel-gpu-tools,tiagovignatti/intel-gpu-tools,mv0/intel-gpu-tools,mv0/intel-gpu-tools,yipdw/intel-gpu-tools,chenxianqin/intel-gpu-tools,erikarn/intel-gpu-tools,chenxianqin/intel-gpu-tools,yipdw/intel-gpu-tools,mv0/intel-gpu-tools,erikarn/intel-gpu-tools,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools