Temporarily disable WPT for RTCPeerConnection-mandatory-getStats

A coming WebRTC CL,
https://webrtc-review.googlesource.com/c/src/+/168190
will make one of the tests to pass, temporarily disable
the test to unblock WebRTC CL roll. Test should be reenabled
with updated expectations once the WebRTC CL is rolled into Chromium.

Bug: webrtc:7061
Change-Id: If334429f2aa0ee34f1a478a7072604081199c4b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2051107Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Commit-Queue: Johannes Kron <kron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#740840}

third_party/blink/web_tests/TestExpectations

@@ -6525,3 +6525,8 @@ crbug.com/1050559 [ Linux ] external/wpt/WebCryptoAPI/derive_bits_keys/hkdf.http
 # the try bot, so we have to skip these tests on Win10 for now to ensure
 # test coverage of other tests.
 crbug.com/1050834 crbug.com/1050838 [ Win10 ] virtual/off-main-thread-css-paint/* [ Skip ]
+
+# Temporarily disable to unblock WebRTC CL roll making it PASS a test.
+crbug.com/webrtc/7061 external/wpt/webrtc/RTCPeerConnection-mandatory-getStats.https.html [ Pass Failure ]
+crbug.com/webrtc/7061 virtual/webrtc-wpt-plan-b/external/wpt/webrtc/RTCPeerConnection-mandatory-getStats.https.html [ Pass Failure ]
+