DOCS-14250 fix cmp operators missing header row

Author: andf-mongodb

source/includes/extracts-agg-operators.yaml

@@ -168,6 +168,9 @@ content: |
       :header-rows: 1
       :widths: 20 80
 
+      * - Name
+        - Description
+
       * - :expression:`$cmp`
 
         - Returns ``0`` if the two values are equivalent, ``1`` if the
@@ -632,12 +635,10 @@ content: |
         - Return the BSON data type of the field.
 
 
-
 ---
 ref: agg-operators-accumulators-group
 content: |
 
-
    .. list-table::
       :header-rows: 1
       :widths: 20 80