Remove unnecessary include

After https://chromium-review.googlesource.com/c/chromium/src/+/1232584,
layout_block.h no longer needs to include ng_constraint_space.h

Change-Id: I9788d6ba0488431facfd3af1eaf6e8f32927ca91
Reviewed-on: https://chromium-review.googlesource.com/1234218
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592519}

third_party/blink/renderer/core/layout/layout_block.h

@@ -27,13 +27,13 @@
 #include <memory>
 #include "third_party/blink/renderer/core/core_export.h"
 #include "third_party/blink/renderer/core/layout/layout_box.h"
-#include "third_party/blink/renderer/core/layout/ng/ng_constraint_space.h"
 #include "third_party/blink/renderer/platform/wtf/list_hash_set.h"
 
 namespace blink {
 
 struct PaintInfo;
 class LineLayoutBox;
+class NGConstraintSpace;
 class WordMeasurement;
 
 typedef WTF::ListHashSet<LayoutBox*, 16> TrackedLayoutBoxListHashSet;