Removed serving primary_tag when members is enabled

no issue

- Content API v2 served primary_tag by default if members flag is enabled
- reference: b2201d4179
- it's safe to remove, because members is behind the dev flag

core/server/api/v2/utils/serializers/output/utils/members.js

@@ -47,6 +47,7 @@ const forPost = (attrs, frame) => {
 
         if (!origInclude || !origInclude.includes('tags')) {
             delete attrs.tags;
+            attrs.primary_tag = null;
         }
     }