Merge branch 'docs/update-prometheus-step' into 'master'

Docs: Update prometheus doc to include new step value

See merge request gitlab-org/gitlab!29194

doc/user/project/integrations/prometheus.md

@@ -309,6 +309,7 @@ The following tables outline the details of expected properties.
 | `label` | string | no, but highly encouraged | Defines the legend-label for the query. Should be unique within the panel's metrics. Can contain time series labels as interpolated variables. |
 | `query` | string | yes if `query_range` is not defined | Defines the Prometheus query to be used to populate the chart/panel. If defined, the `query` endpoint of the [Prometheus API](https://prometheus.io/docs/prometheus/latest/querying/api/) will be utilized. |
 | `query_range` | string | yes if `query` is not defined | Defines the Prometheus query to be used to populate the chart/panel. If defined, the `query_range` endpoint of the [Prometheus API](https://prometheus.io/docs/prometheus/latest/querying/api/) will be utilized. |
+| `step` | number | no, value is calculated if not defined | Defines query resolution step width in float number of seconds. Metrics on the same panel should use the same `step` value. |
 
 ##### Dynamic labels