Include the ml inference aggregation doc (#59219)

Add to the list of pipeline aggregations

docs/reference/aggregations/pipeline.asciidoc

@@ -288,3 +288,4 @@ include::pipeline/normalize-aggregation.asciidoc[]
 include::pipeline/serial-diff-aggregation.asciidoc[]
 include::pipeline/stats-bucket-aggregation.asciidoc[]
 include::pipeline/extended-stats-bucket-aggregation.asciidoc[]
+include::pipeline/inference-bucket-aggregation.asciidoc[]