(DOCSP-45304) fixes build error

Author: carriecwk

source/reference/api/snapshots/take-an-on-demand-snapshot.txt

@@ -51,16 +51,16 @@ Request Path Parameters
 Request Query Parameters
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
-The following query parameters are optional:
-
 .. list-table::
    :widths: 20 14 11 45 10
    :header-rows: 1
    :stub-columns: 1
 
    * - Name
      - Type
+     - Necessity
      - Description
+     - Example
 
    * - retentionDays
      - number