Remove TSAN suppression related to webrtc::EventPosix

Remove TSAN suppression related to webrtc::EventPosix

A race used to be detected by TSAN when running
WebRtcInternalsBrowserTest.WithRealPeerConnectionCall

This test is currently disabled due to flakiness (see crbug.com/272413).
However, the webrtc::EventPosix issues were refactored and no longer cause races
with that (disabled) test (or any other test).

BUG=246970
Committed: https://crrev.com/31cb44c6430327dff8765ebaf8f51f18aa1d7045
Cr-Commit-Position: refs/heads/master@{#325204}

[Guido Urdaneta, 2015-04-14 15:12:21]

guidou@chromium.org changed reviewers:
+ henrika@chromium.org, pbos@chromium.org

[henrika (OOO until Aug 14), 2015-04-14 16:32:38]

LGTM

[pbos, 2015-04-14 20:49:25]

lgtm

[Guido Urdaneta, 2015-04-15 07:36:55]

The CQ bit was checked by guidou@chromium.org

[commit-bot: I haz the power, 2015-04-15 07:37:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1088923003/1

[commit-bot: I haz the power, 2015-04-15 07:41:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-15 07:42:55]

Patchset 1 (id:??) landed as
https://crrev.com/31cb44c6430327dff8765ebaf8f51f18aa1d7045
Cr-Commit-Position: refs/heads/master@{#325204}