Update AddCampaigns example to illustrate Display Expansion setting (#590)

Author: jradcliff

google-ads-examples/src/main/java/com/google/ads/googleads/examples/basicoperations/AddCampaigns.java

@@ -145,7 +145,9 @@ private void runExample(GoogleAdsClient googleAdsClient, long customerId) {
           NetworkSettings.newBuilder()
               .setTargetGoogleSearch(true)
               .setTargetSearchNetwork(true)
-              .setTargetContentNetwork(false)
+              // Enables Display Expansion on Search campaigns. See
+              // https://support.google.com/google-ads/answer/7193800 to learn more.
+              .setTargetContentNetwork(true)
               .setTargetPartnerSearchNetwork(false)
               .build();