[cairo] cairo_surface_write_to_png() docs

[Behdad Esfahbod]

They currently say:

 * Return value: %CAIRO_STATUS_SUCCESS if the PNG file was written
 * successfully.  Otherwise, %CAIRO_STATUS_NO_MEMORY is returned if
 * memory could not be allocated for the operation,
 * %CAIRO_STATUS_SURFACE_TYPE_MISMATCH if the surface does not have
 * pixel contents.

Shouldn't the final remark about type-mismatch be removed?

-- 
behdad
http://behdad.org/

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