Import org.junit.Assert instead of junit.framework.Assert.

This fixed the warning:
app/webrtc/java/testcommon/src/org/webrtc/PeerConnectionTest.java:46: warning: [deprecation] Assert in junit.framework has been deprecated
import static junit.framework.Assert.*;

R=glaznev@webrtc.org, pthatcher@webrtc.org
BUG=none

Review URL: https://webrtc-codereview.appspot.com/50209004

Cr-Commit-Position: refs/heads/master@{#9356}
diff --git a/talk/app/webrtc/java/testcommon/src/org/webrtc/PeerConnectionTest.java b/talk/app/webrtc/java/testcommon/src/org/webrtc/PeerConnectionTest.java
index 224225c..02a76da 100644
--- a/talk/app/webrtc/java/testcommon/src/org/webrtc/PeerConnectionTest.java
+++ b/talk/app/webrtc/java/testcommon/src/org/webrtc/PeerConnectionTest.java
@@ -43,7 +43,7 @@
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
-import static junit.framework.Assert.*;
+import static org.junit.Assert.*;
 
 /** End-to-end tests for PeerConnection.java. */
 public class PeerConnectionTest {