Disable auto-block-size-inflow.https.html

This test has started to flake recently, disabling during investigation.

Bug: chromium:868706
Tbr: tommycli@chromium.org
Change-Id: Icb9767c98885c76dece2f4b39449bf6e04a6ddcb
Reviewed-on: https://chromium-review.googlesource.com/1155993
Commit-Queue: Peter Boström <pbos@chromium.org>
Reviewed-by: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579278}

third_party/WebKit/LayoutTests/TestExpectations

@@ -4875,3 +4875,4 @@ crbug.com/824539 [ Android ] virtual/layout_ng/fast/block/margin-collapse/019.ht
 
 # Sheriff 2018-07-30
 crbug.com/866166 virtual/gpu-rasterization/images/color-profile-image-filter-all.html [ Pass Timeout ]
+crbug.com/868706 external/wpt/css/css-layout-api/auto-block-size-inflow.https.html [ Pass Failure ]