Update understanding-ab2d-data.md (#68)

fixed typo to add space between "stand-alone" and "Prescription Drug
Plan (PDP) sponsors."

previously: stand-alonePrescription Drug Plan (PDP) sponsors 
new: stand-alone Prescription Drug Plan (PDP) sponsors

## 🎫 Ticket

no ticket made since this is such a small change

## 🛠 Changes

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## ℹ️ Context

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understanding-ab2d-data.md

@@ -31,7 +31,7 @@ active-nav: understanding-the-data-nav
                     </li>
                 </ul>
                 <p>
-                    These claims contain valuable information about enrollee health, which can help fill any gaps in the health records available to stand-alonePrescription Drug Plan (PDP) sponsors.
+                    These claims contain valuable information about enrollee health, which can help fill any gaps in the health records available to stand-alone Prescription Drug Plan (PDP) sponsors.
                 </p>
             </div>
             <div class="col-lg-6">
@@ -109,4 +109,4 @@ active-nav: understanding-the-data-nav
             </div>
         </div>    
     </div>
-</section>    
+</section>