[DET-62] Add manual trigger option to Data Observability monitor docs (#37570)

* Updated DO monitor docs to support manual triggers

* removed settings and updated wording

* Update content/en/monitors/types/data_observability.md

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* updated docs with more information to help users understand the limitations of this feature

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: brkelley

content/en/monitors/types/data_observability.md

@@ -196,6 +196,7 @@ Set how often the monitor evaluates your data:
 
 - **Hourly**: The monitor runs every hour.
 - **Daily**: The monitor runs once per day.
+- **Manual**: The monitor runs only when triggered programmatically. Trigger these monitors using the [Data Observability API][10] on a schedule so enough historical data can accumulate for modeling to be useful. Currently, the UI does not support default metrics like row counts and freshness, so this workflow only applies to custom or column-level metrics.
 
 ### Set alert conditions
 
@@ -298,3 +299,4 @@ On a monitor's status page, click **Annotate Bounds**, select a time range on th
 [7]: https://app.datadoghq.com/data-obs/monitors
 [8]: /monitors/configuration/?tab=thresholdalert#thresholds
 [9]: /help/
+[10]: /api/latest/data-observability/