Fix test failure expectation on document-policy-unoptimized-images-cached-image.html

Previously width attribute on iframe is changed from 440 to 500, but the
test expectation png files are not updated in CL(https://chromium-review.googlesource.com/c/chromium/src/+/1531354).

This CL updates the expectation files.

Bug: 922951
Change-Id: Ibea9a655750d0851e576be67872f6a6d83cea25a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2090612
Commit-Queue: Charlie Hu <chenleihu@google.com>
Reviewed-by: Ian Clelland <iclelland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749259}

third_party/blink/web_tests/TestExpectations

@@ -5511,7 +5511,6 @@ crbug.com/922951 virtual/text-antialias/international/inline-plaintext-relayout-
 crbug.com/922951 http/tests/cache/subresource-fragment-identifier.html [ Failure Pass Timeout Crash ]
 crbug.com/922951 http/tests/devtools/tracing/timeline-network-received-data.js [ Failure Pass Timeout Crash ]
 crbug.com/922951 http/tests/history/back-to-post.html [ Failure Pass Timeout Crash ]
-crbug.com/922951 http/tests/images/document-policy-unoptimized-images-cached-image.html [ Failure Pass Timeout Crash ]
 crbug.com/922951 http/tests/security/offscreencanvas-placeholder-read-blocked-no-crossorigin.html [ Failure Pass Timeout Crash ]
 crbug.com/922951 http/tests/security/cookies/basic.html [ Failure Pass Timeout Crash ]
 crbug.com/922951 http/tests/webaudio/autoplay-crossorigin.html [ Failure Pass Timeout Crash ]