Update http.mdx

doc-surrealdb_versioned_docs/version-latest/querying/graphql/http.mdx

@@ -104,7 +104,7 @@ The GraphQL endpoint enables use of GraphQL queries to interact with your data.
 
 ### Example usage
 ```bash title="Request"
-curl -X POST -u "root:root" -H "NS: mynamespace" -H "DB: mydatabase" -H "Accept: application/json" -d '{"query": "{ person(filter: {age: {age_gt: 18}}) { id name age } }"}' http://localhost:8000/graphql
+curl -X POST -u "root:root" -H "surreal-ns: mynamespace" -H "surreal-db: mydatabase" -H "Accept: application/json" -d '{"query": "{ person(filter: {age: {age_gt: 18}}) { id name age } }"}' http://localhost:8000/graphql
 ```
 
 ```json title="Response"