Separate multiple DNS addresses with newlines.

Bug: b/65037256
Test: make -j40 RunSettingsRoboTests
Change-Id: I4b0709648f8e236177ea73338cfb0d42a5971c06

src/com/android/settings/wifi/details/WifiDetailPreferenceController.java

@@ -433,7 +433,7 @@ public class WifiDetailPreferenceController extends AbstractPreferenceController
         String dnsServers = mLinkProperties.getDnsServers().stream()
                 .filter(Inet4Address.class::isInstance)
                 .map(InetAddress::getHostAddress)
-                .collect(Collectors.joining(","));
+                .collect(Collectors.joining("\n"));
 
         // Update UI.
         updatePreference(mIpAddressPref, ipv4Address);