serial-diff-aggregation.asciidoc: fix a mistake (#17950)

docs/reference/aggregations/pipeline/serial-diff-aggregation.asciidoc

@@ -47,7 +47,7 @@ A `serial_diff` aggregation looks like this in isolation:
 }
 --------------------------------------------------
 
-.`moving_avg` Parameters
+.`serial_diff` Parameters
 |===
 |Parameter Name |Description |Required |Default Value
 |`buckets_path` |Path to the metric of interest (see <<buckets-path-syntax, `buckets_path` Syntax>> for more details |Required |