doc: upgrade StanfordImporter caveats from some to minor.

It now delegates to Assimp for ASCII files, along with StlImporter that
does the same but was already marked as having minor caveats. Better
than nothing, and it's not my problem that Assimp leaks and crashes like
mad on broken files.

doc/file-formats.dox

@@ -539,7 +539,7 @@ Together with @ref file-formats-image-importers "image importers" derived from
 <th rowspan="2">Stanford PLY<br/>(`*.ply`)</th>
 <td rowspan="2">`StanfordImporter`</td>
 <td>@ref Trade::StanfordImporter "StanfordImporter"</td>
-<td class="m-text-center m-warning">@ref Trade-StanfordImporter-behavior "some"</td>
+<td class="m-text-center m-success">@ref Trade-StanfordImporter-behavior "minor"</td>
 <td class="m-text-center">@m_span{m-text m-dim} none @m_endspan </td>
 <td class="m-text-center"></td>
 </tr>