test: Update reference images due to previous change to _cairo_color_compute_shorts

The previous change was in b62710d4f8
We just forgot to update the reference images at the time so there
have been false failure results in the test suite until now.

test/set-source.c

@@ -38,9 +38,7 @@ static cairo_test_status_t
 draw (cairo_t *cr, int width, int height)
 {
     int i;
-    /* This color value might need to change in the future when we fix
-     * the rounding in cairo-color.c */
-    uint32_t color = 0x7f19334C;
+    uint32_t color = 0x8019334c;
     cairo_surface_t *surface;
     cairo_pattern_t *pattern;