[librsvg/rustification] Test 21 for gradients also passes; regenerate ref image

[Federico Mena Quintero <federico src gnome org>]

commit f3aac518feed53ad29d04918e08ec08802cf18e3
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri Nov 11 17:17:29 2016 -0600

    Test 21 for gradients also passes; regenerate ref image

 .../reftests/svg1.1/pservers-grad-21-b-ref.png     |  Bin 12246 -> 11563 bytes
 1 files changed, 0 insertions(+), 0 deletions(-)
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diff --git a/tests/fixtures/reftests/svg1.1/pservers-grad-21-b-ref.png 
b/tests/fixtures/reftests/svg1.1/pservers-grad-21-b-ref.png
index 207c6e7..16ad4fb 100644
Binary files a/tests/fixtures/reftests/svg1.1/pservers-grad-21-b-ref.png and 
b/tests/fixtures/reftests/svg1.1/pservers-grad-21-b-ref.png differ