Skip testTetherClatUdp before S

The test does not pass on R.

Bug: 234727688
Test: atest EthernetTetheringTest
Change-Id: I831859e521b026ed4acb84de5857a7d3ec318ba5

Tethering/tests/integration/src/android/net/EthernetTetheringTest.java

@@ -1329,6 +1329,7 @@ public class EthernetTetheringTest {
     }
 
     @Test
+    @IgnoreUpTo(Build.VERSION_CODES.R)
     public void testTetherClatUdp() throws Exception {
         // CLAT only starts on IPv6 only network.
         initializeTethering(toList(TEST_IP6_ADDR), toList(TEST_IP6_DNS));