chore(nimbus): Change text sizing of 'No Deliveries' text on the feature page. (#13772)

Because

- We want the "No Deliveries" callout to match the the styling thats in
the QA Runs table

This commit

- Updates the callout to match styling

Fixes #13770

Author: b4handjr

experimenter/experimenter/nimbus_ui/templates/nimbus_experiments/features.html

@@ -99,9 +99,9 @@ <h5 class="fw-semibold">
                   </tr>
                 {% empty %}
                   <tr>
-                    <td colspan="12" class="fw-semibold text-center p-4">
-                      <h4>No Deliveries</h4>
-                    </td>
+                    <tr>
+                      <td colspan="11" class="text-center text-muted py-5">No Deliveries</td>
+                    </tr>
                   </tr>
                 {% endfor %}
               </tbody>