Update MSAN expectations for external/wpt/picture-in-picture/idlharness.window.html

Failure example:
https://ci.chromium.org/buildbot/chromium.webkit/WebKit%20Linux%20Trusty%20MSAN/9598

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 873045
Change-Id: I97f130469c20017f4fb4d336845bf89195729b1e
Reviewed-on: https://chromium-review.googlesource.com/1187126Reviewed-by: Sahel Sharify <sahel@chromium.org>
Commit-Queue: Sahel Sharify <sahel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585610}

third_party/WebKit/LayoutTests/MSANExpectations

@@ -186,7 +186,7 @@ crbug.com/869818 [ Linux ] http/tests/background_fetch/block-cors-preflights.htt
 
 # Disabled by sheriff due to repeated flakes
 crbug.com/873045 [ Linux ] external/wpt/WebCryptoAPI/idlharness.https.any.worker.html [ Pass Failure Timeout ]
+crbug.com/873045 [ Linux ] external/wpt/picture-in-picture/idlharness.window.html [ Pass Failure Timeout ]
 # Also flaking according to crbug.com/873045 but mentioned in existing entries above:
-# external/wpt/picture-in-picture/idlharness.window.html
 # external/wpt/notifications/idlharness.https.any.worker.html
 # external/wpt/xhr/idlharness.any.worker.html