Update NavigationBrowserTest.UncacheablePost

This test started failing with the BackForwardCache after:
https://chromium-review.googlesource.com/c/chromium/src/+/1761051

It goes back to a page with no-cache, no-store, must-revalidate.
This page is cached, while it shouldn't...

TBR=altimin@chromium.org

Bug: 990354
Change-Id: I355be9f434c125890817b5c1a1b402c1a6f9b2d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1778487Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#692120}

testing/buildbot/filters/bfcache.content_browsertests.filter

@@ -67,6 +67,9 @@
 # once. The navigations are now committing synchronously, which is too fast.
 -NavigationControllerBrowserTest.HistoryBackTwiceFromRendererWithoutUserGesture
 
+# Page with no-cache, no-store, must-revalidate shouldn't be cached.
+-NavigationControllerBrowserTest.UncacheablePost
+
 # Test expects the RenderFrameHost to be deleted after a navigation. It is now
 # stored into the BackForwardCache instead. It isn't deleted.
 -RenderFrameHostManagerTest.CleanupOnCrossProcessNavigation
@@ -126,4 +129,3 @@
 # https://crbug.com/992891
 -WebContentsSplitCacheBrowserTestEnabled.SplitCacheDedicatedWorkerScripts/1
 -WebContentsSplitCacheBrowserTestEnabled.SplitCacheDedicatedWorkerScripts/0
-