Ignore test that times out on MSAN

See attached bug.

TBR: rouslan@chromium.org
Bug: 1115091
Change-Id: I54a433ed5ce6321df2d906fa55584ed51ca55365
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391607Reviewed-by: Dana Fried <dfried@chromium.org>
Commit-Queue: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803983}

third_party/blink/web_tests/TestExpectations

@@ -6644,3 +6644,6 @@ crbug.com/1122106 external/wpt/webrtc/protocol/crypto-suite.https.html [ Pass Ti
 crbug.com/1122742 http/tests/devtools/sources/debugger/source-frame-inline-breakpoint-decorations.js [ Pass Timeout ]
 
 crbug.com/1122582 external/wpt/html/cross-origin-opener-policy/coop-csp-sandbox-navigate.https.html [ Pass Failure ]
+
+# Sheriff 2020-09-02
+crbug.com/1115091 [ Linux ] external/wpt/payment-request/secure-payment-confirmation.https.html [ Pass Timeout ]