BCDA-8392-add-runout-description (#220)

## 🎫 Ticket

https://jira.cms.gov/browse/BCDA-8392

## 🛠 Changes

Added runout data description.

## ℹ️ Context

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non-technical audience. -->

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  - Adds a new software dependency or dependencies.
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## 🧪 Validation

Site build and review locally.

---------

Co-authored-by: Greg Pfadenhauer <[email protected]>

build.html

@@ -247,6 +247,9 @@ <h2>
           <h2>
             Request runouts data with /Group and `runout`
           </h2>
+          <div class="ds-u-font-size--base">
+            Use /Group/runout at the beginning of a new Performance Year (PY) to retrieve runouts data for the the previous PY. Runouts data includes claims data for Medicare enrollees who were attributed to your model entity the previous year but not the current year. These claims will have a service date no later than December 31 of the previous year.
+          </div>
           <div class="ds-u-font-size--base">
             {% include build/requesting_data_runouts.html %}
           </div>