[skia] Remove image filter legacy flags

Change-Id: Iefd07280198060ac7ed46d326ea0379f2ca6df3d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5920776
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Cr-Commit-Position: refs/heads/main@{#1370373}

css/filter-effects/backdrop-filter-plus-filter.html

@@ -4,6 +4,7 @@
 <link rel="author" href="mailto:masonf@chromium.org">
 <link rel="help" href="https://drafts.fxtf.org/filter-effects-2/#BackdropFilterProperty">
 <link rel="match"  href="backdrop-filter-plus-filter-ref.html">
+<meta name=fuzzy content="maxDifference=0-1; totalPixels=0-210">
 
 <p>Expected: A green box with an overlapping purple box.<br>
 The overlapping portion of the boxes should be bright magenta.<br>