Update comments in conversion upload examples to clarify source is optional (#491)

Author: jradcliff

google-ads-examples/src/main/java/com/google/ads/googleads/examples/remarketing/UploadConversionEnhancement.java

@@ -160,8 +160,6 @@ private void runExample(
     // Creates a user identifier using sample values for the user address.
     UserIdentifier addressIdentifier =
         UserIdentifier.newBuilder()
-            // User identifiers for conversion enhancements MUST use first party data.
-            .setUserIdentifierSource(UserIdentifierSource.FIRST_PARTY)
             .setAddressInfo(
                 OfflineUserAddressInfo.newBuilder()
                     .setHashedFirstName(normalizeAndHash(sha256Digest, "Joanna"))
@@ -172,6 +170,8 @@ private void runExample(
                     .setState("CA")
                     .setPostalCode("94043")
                     .setCountryCode("US"))
+            // Optional: Specifies the user identifier source.
+            .setUserIdentifierSource(UserIdentifierSource.FIRST_PARTY)
             .build();
 
     // Creates a user identifier using the hashed email address.

google-ads-examples/src/main/java/com/google/ads/googleads/examples/remarketing/UploadConversionWithIdentifiers.java

@@ -166,9 +166,9 @@ private void runExample(
     String hashedEmail = normalizeAndHashEmailAddress(sha256Digest, emailAddress);
     UserIdentifier userIdentifier =
         UserIdentifier.newBuilder()
-            // User identifiers for conversion enhancements MUST use first party data.
-            .setUserIdentifierSource(UserIdentifierSource.FIRST_PARTY)
             .setHashedEmail(hashedEmail)
+            // Optional: Specifies the user identifier source.
+            .setUserIdentifierSource(UserIdentifierSource.FIRST_PARTY)
             .build();
 
     // Adds the user identifier to the conversion.