feat: use OPEN_AI instead of OpenAI for the provider enum

Author: mjfwebb

modules/ROOT/pages/directives/indexes-and-constraints.adoc

@@ -379,7 +379,7 @@ Requires credentials for the plugin.
 type Product @vector(indexes: [{
   indexName: "productDescriptionIndex",
   embeddingProperty: "descriptionVector",
-  provider: OpenAI,  # Assuming this is configured in the server
+  provider: OPEN_AI,  # Assuming this is configured in the server
   queryName: "searchByPhrase"
 }]) {
   id: ID!
@@ -411,4 +411,4 @@ query SearchProductsByPhrase($phrase: String!) {
 ----
 
 First, the query passes the query phrase argument `$phrase` to the GenAI plugin and lets it generate a vector embedding for the phrase.
-Then it returns all `Product` nodes with a vector embedding on their `descriptionVector` property which are similar to the vector embedding generated by the plugin.
+Then it returns all `Product` nodes with a vector embedding on their `descriptionVector` property which are similar to the vector embedding generated by the plugin.