Revert of WebRTC: Re-enable 30s datachannel telemetry test. (patchset P…

…issandshittium#1 id:1 of https://codereview.chromium.org/2908383002/ )

Reason for revert:
Test timing out on many of the Desktop perf bots such as...

Linux Perf
Mac 10.11 Perf.Mac Pro 10.11Perf
Win 7 Interl GPU Perf

and about 10 more.

Original issue's description:
> WebRTC: Re-enable 30s datachannel telemetry test.
>
> BUG=chromium:726811
>
> Review-Url: https://codereview.chromium.org/2908383002
> Cr-Commit-Position: refs/heads/master@{#475797}
> Committed: https://chromium.googlesource.com/chromium/src/+/0e5657e03379575203b9617d955e1c410d3db7f2

TBR=charliea@chromium.org,nednguyen@google.com,ehmaldonado@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=chromium:726811

Review-Url: https://codereview.chromium.org/2927673002
Cr-Commit-Position: refs/heads/master@{#477483}

tools/perf/page_sets/webrtc_cases.py

@@ -153,3 +153,7 @@ def SetExpectations(self):
     self.DisableStory('audio_call_isac/1600_10s',
                       [story.expectations.ALL],
                       'crbug.com/468732')
+
+    self.DisableStory('30s_datachannel_transfer',
+                      [story.expectations.ALL_DESKTOP],
+                      'crbug.com/726811')