Fix WebRTC-ConferenceTemporalLayers test config

Remove ios, add android webview.

Bug: 1000023
Change-Id: Iace7f258104df5d46f51c20e3ceb19f43120e14f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1795908
Commit-Queue: Erik Språng <sprang@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Auto-Submit: Erik Språng <sprang@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695231}

testing/variations/fieldtrial_testing_config.json

@@ -6872,8 +6872,8 @@
                 "mac",
                 "chromeos",
                 "linux",
-                "ios",
-                "android"
+                "android",
+                "android_webview"
             ],
             "experiments": [
                 {