[Sheriff] Update expectations for fast/forms/suggested-value.html

webkit_layout_tests failing on Win7

https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win7/builds/56163

TBR=mkwst@chromium.org

Bug: 770971
Notry: True
Change-Id: I35034ffbbd1a0d727920855544b8d8519895156d
Reviewed-on: https://chromium-review.googlesource.com/696131Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505860}

third_party/WebKit/LayoutTests/TestExpectations

@@ -3720,3 +3720,6 @@ crbug.com/767892 [ Win Linux Mac ] virtual/mojo-loading/http/tests/devtools/star
 
 # Sheriff failures 2017-09-29
 crbug.com/770362 [ Linux Debug ] virtual/threaded/animations/unanimated-style.html [ Pass Timeout ]
+
+# Sheriff failures 2017-10-02
+crbug.com/770971 [ Win7 ] fast/forms/suggested-value.html [ Pass Failure ]