Remove Assert lint suppression.

BUG=webrtc:6597
NOTRY=True

Review-Url: https://codereview.webrtc.org/2668963002
Cr-Commit-Position: refs/heads/master@{#16460}

webrtc/sdk/android/api/org/webrtc/NetworkMonitorAutoDetect.java

@@ -263,7 +263,10 @@ public class NetworkMonitorAutoDetect extends BroadcastReceiver {
           // ConnectivityManager.getDefaultNetwork() though this
           // may give confusing results with VPNs and is only
           // available with Android Marshmallow.
-          assert defaultNetId == INVALID_NET_ID;
+          if (defaultNetId != INVALID_NET_ID) {
+            throw new RuntimeException(
+                "Multiple connected networks of same type are not supported.");
+          }
           defaultNetId = networkToNetId(network);
         }
       }