add .btn-inverse removal to migration guide; fixes #12538

docs/migration.html

@@ -350,6 +350,11 @@ lead: "Guidance on how to upgrade from Bootstrap v2.x to v3.x with emphasis on m
           <td><code>.input-block-level</code></td>
           <td>No direct equivalent, but <a href="../css/#forms-controls">forms controls</a> are similar.</td>
         </tr>
+        <tr>
+          <td>Inverse buttons</td>
+          <td><code>.btn-inverse</code></td>
+          <td class="text-muted">N/A</td>
+        </tr>
         <tr>
           <td>Fluid row</td>
           <td><code>.row-fluid</code></td>