Be specific about the exposition formats supported (#14370)

* Be specific about the exposition formats supported

* Remove references to configuration of actual format

As those are no longer needed after #14445.

openmetrics/README.md

@@ -2,10 +2,12 @@
 
 ## Overview
 
-Extract custom metrics from any OpenMetrics endpoints.
+Extract custom metrics from any OpenMetrics or Prometheus endpoints.
 
 <div class="alert alert-warning">All the metrics retrieved by this integration are considered <a href="https://docs.datadoghq.com/developers/metrics/custom_metrics">custom metrics</a>.</div>
 
+The integration is compatible with both the [Prometheus exposition format][12] as well as with the [OpenMetrics specification][13].
+
 ## Setup
 
 Follow the instructions below to install and configure this check for an Agent running on a host. For containerized environments, see the [Autodiscovery Integration Templates][1] for guidance on applying these instructions.
@@ -22,7 +24,7 @@ For each instance the following parameters are required:
 
 | Parameter        | Description                                                                                                                                                                                                                                                              |
 | ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
-| `openmetrics_endpoint` | The URL where your application metrics are exposed by OpenMetrics (must be unique).                                                                                                                         |
+| `openmetrics_endpoint` | The URL where your application metrics are exposed in Prometheus or OpenMetrics format (must be unique).                                                                                                                         |
 | `namespace`      | The namespace to prepend to all metrics.                                                                                                                                                                                                                                 |
 | `metrics`        | A list of metrics to retrieve as custom metrics. Add each metric to the list as `metric_name` or `metric_name: renamed` to rename it. The metrics are interpreted as regular expressions. Use `.*` as a wildcard (`metric.*`) to fetch all matching metrics. **Note**: Regular expressions can potentially send a lot of custom metrics. |
 
@@ -78,3 +80,5 @@ Need help? Contact [Datadog support][8].
 [9]: https://docs.datadoghq.com/agent/openmetrics/
 [10]: https://docs.datadoghq.com/developers/openmetrics/
 [11]: https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#suffixes
+[12]: https://prometheus.io/docs/instrumenting/exposition_formats/#text-based-format
+[13]: https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#suffixes