Add scripted metrics to serverless differences (#52)

* Update serverless-differences.mdx

* Update serverless-differences.mdx

* Update serverless-differences.mdx

* Update serverless-differences.mdx

* Add note to Aggregations page

Author: marciw

serverless/pages/explore-your-data-the-aggregations-api.mdx

@@ -17,7 +17,9 @@ Aggregations help you answer questions like:
 ((es)) organizes aggregations into three categories:
 
 * [Metric](((ref))/search-aggregations-metrics.html) aggregations that calculate metrics,
-    such as a sum or average, from field values.
+    such as a sum or an average, from field values. Note that
+    [scripted metric aggregations](((ref))/search-aggregations-metrics-scripted-metric-aggregation.html) 
+    are not available in serverless ((es)).
 
 * [Bucket](((ref))/search-aggregations-bucket.html) aggregations that
     group documents into buckets, also called bins, based on field values, ranges,

serverless/pages/serverless-differences.mdx

@@ -30,9 +30,11 @@ text="data stream lifecycle"/>**.
 
   Serverless Elasticsearch manages the underlying Elastic cluster for you, optimizing nodes, shards, and replicas for your use case. 
   Because of this, various management and monitoring APIs, API parameters and settings are not available on Serverless.
+  <br/>
+- [Scripted metric aggregations](((ref))/search-aggregations-metrics-scripted-metric-aggregation.html) are not available.
 
 <DocCallOut title="Other limitations" color="warning">
 
 For serverless technical preview limitations, refer to <DocLink slug="/serverless/elasticsearch/technical-preview-limitations" text="Technical preview limitations"/>. 
 
-</DocCallOut>
+</DocCallOut>