Add experimental + fix docs

Author: jan-elastic

docs/reference/esql/functions/grouping-functions.asciidoc

@@ -9,7 +9,7 @@ The <<esql-stats-by>> command supports these grouping functions:
 
 // tag::group_list[]
 * <<esql-bucket>>
-* <<esql-categorize>>
+* experimental:[] <<esql-categorize>>
 // end::group_list[]
 
 include::layout/bucket.asciidoc[]

x-pack/plugin/esql/qa/testFixtures/src/main/resources/docs.csv-spec

@@ -686,10 +686,10 @@ FROM sample_data
 | SORT category
 ;
 
-// tag::docsCategorize[]
+// tag::docsCategorize-result[]
 count:long | category:keyword
          3 | .*?Connected.+?to.*?
          3 | .*?Connection.+?error.*?
          1 | .*?Disconnected.*?
-// end::docsCategorize[]
+// end::docsCategorize-result[]
 ;