Revert "[LayoutNG] Don't truncate margins after spanners."

This reverts commit 430b7621a298f2744248997692a2d8f68224fa67.

Reason for revert: Failing builder https://ci.chromium.org/p/chromium/builders/ci/linux-trusty-rel

Original change's description:
> [LayoutNG] Don't truncate margins after spanners.
>
> A column spanner forcefully breaks a column, so any leading margins on
> content right after the spanner shouldn't be discarded.
>
> Bug: 829028
> Change-Id: I767466677d72be2760306ddd531e847f52cfa8ca
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2445482
> Reviewed-by: Alison Maher <almaher@microsoft.com>
> Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
> Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#813892}

TBR=ikilpatrick@chromium.org,mstensho@chromium.org,almaher@microsoft.com

Change-Id: I535ec21071aacd85f22968286e0f920fd2870324
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 829028
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2450062
Reviewed-by: Nohemi Fernandez <fernandex@chromium.org>
Commit-Queue: Nohemi Fernandez <fernandex@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814142}
diff --git a/css/css-multicol/multicol-span-all-015.html b/css/css-multicol/multicol-span-all-015.html
deleted file mode 100644
index 041c211..0000000
--- a/css/css-multicol/multicol-span-all-015.html
+++ /dev/null
@@ -1,16 +0,0 @@
-<!DOCTYPE html>
-<link rel="author" title="Morten Stenshorne" href="mailto:mstensho@chromium.org">
-<link rel="help" href="https://www.w3.org/TR/css-multicol-1/#spanning-columns">
-<link rel="help" href="https://www.w3.org/TR/css-break-3/#break-margins">
-<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
-<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
-<div style="columns:2; column-gap:0; width:100px; background:red;">
-  <div style="height:30px;"></div>
-  <div style="height:30px; background:green;"></div>
-  <div>
-    <div style="column-span:all; height:40px; background:green;">
-      <div style="width:50px; height:40px; background:red;"></div>
-    </div>
-  </div>
-  <div style="margin-top:-70px; height:130px; background:green;"></div>
-</div>