Disable the flaky form-action-src-default-ignored-with-redirect on Win7

Bug: 854538
Change-Id: I1e33574edf070dc93cf897faab75a0e53df39dd8
TBR: mkwst@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/1109959Reviewed-by: Martin Šrámek <msramek@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Martin Šrámek <msramek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569258}

third_party/WebKit/LayoutTests/TestExpectations

@@ -4734,3 +4734,5 @@ crbug.com/853360 [ Mac ] fast/forms/select/menulist-appearance-rtl.html [ Failur
 # Sheriff 2018-06-18
 crbug.com/853852 [ Linux ] virtual/threaded/external/wpt/feature-policy/experimental-features/vertical-scroll-wheel-block-manual.tentative.html [ Pass Timeout ]
 crbug.com/854053 [ Mac10.13 Debug ] virtual/threaded/fast/animationworklet/animation-worklet-scroll-timeline.html [ Pass Crash ]
+
+crbug.com/854538 [ Win7 ] http/tests/security/contentSecurityPolicy/1.1/form-action-src-default-ignored-with-redirect.html [ Skip ]