update functions counter

x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/esql/60_usage.yml

@@ -92,7 +92,7 @@ setup:
   - gt: {esql.functions.to_long: $functions_to_long}
   - match: {esql.functions.coalesce: $functions_coalesce}
   # Testing for the entire function set isn't feasbile, so we just check that we return the correct count as an approximation.
-  - length: {esql.functions: 122} # check the "sister" test below for a likely update to the same esql.functions length check
+  - length: {esql.functions: 123} # check the "sister" test below for a likely update to the same esql.functions length check
 
 ---
 "Basic ESQL usage output (telemetry) non-snapshot version":