Correct interpretation of output rotation

This fixes grim to treat the rotations as counterclockwise and applied
to the surface. This became necessary because wlroots recently corrected
its rotation similarly in swaywm/wlroots#2023.

render.c

@@ -104,7 +104,7 @@ cairo_surface_t *render(struct grim_state *state, struct grim_box *geometry,
 		cairo_matrix_translate(&matrix,
 			(double)output->geometry.width / 2,
 			(double)output->geometry.height / 2);
-		cairo_matrix_rotate(&matrix, -get_output_rotation(output->transform));
+		cairo_matrix_rotate(&matrix, get_output_rotation(output->transform));
 		cairo_matrix_scale(&matrix,
 			(double)raw_output_width / output_width * output_flipped_x,
 			(double)raw_output_height / output_height * output_flipped_y);