Silence RTCPeerConnection-getStats on more bots

Likely these are bots without H.264 support.

No-Try: true
Bug: 1092721
Change-Id: Ie0a8e17998217fe8caadc5cd509afb9d15439b5c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2236439
Auto-Submit: Harald Alvestrand <hta@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776473}

third_party/blink/web_tests/TestExpectations

@@ -6746,9 +6746,11 @@ crbug.com/1091250 [ Win10 ] virtual/cors/http/tests/misc/resource-timing-sizes-m
 crbug.com/1091948 [ Linux ] external/wpt/html/canvas/element/manual/fill-and-stroke-styles/canvas_colorsandstyles_createlineargradient_001.htm [ Pass Timeout ]
 crbug.com/1092091 [ Mac ] virtual/dark-color-scheme/datetimelocal-picker/datetimelocal-open.html [ Pass Failure ]
 
-# Test giving differing results on different Mac build bots
+# Test giving differing results on different build bots
 crbug.com/1092721 [ Mac ] virtual/webrtc-wpt-plan-b/external/wpt/webrtc/RTCPeerConnection-getStats.https.html [ Pass Failure ]
 crbug.com/1092721 [ Mac ] external/wpt/webrtc/RTCPeerConnection-getStats.https.html [ Pass Failure ]
+crbug.com/1092721 [ Linux ] virtual/webrtc-wpt-plan-b/external/wpt/webrtc/RTCPeerConnection-getStats.https.html [ Pass Failure ]
+crbug.com/1092721 [ Linux ] external/wpt/webrtc/RTCPeerConnection-getStats.https.html [ Pass Failure ]
 
 # Sheriff 2020-06-06
 crbug.com/1091843 fast/canvas/color-space/canvas-createImageBitmap-p3.html [ Pass Failure ]