Update SUPPORTED_MODELS.md (openvinotoolkit#1784)

This should close openvinotoolkit#264. I verified gemma-7b-it with GenAI
text_generation following the instructions in openvinotoolkit#259. It doesn't fail and
outputs a reasonable response.

Co-authored-by: huanligong <huanli.gong@duke.edu>

Author: Huanli-Gong

SUPPORTED_MODELS.md

@@ -24,6 +24,7 @@
       <td>
         <ul>
           <li><a href="https://huggingface.co/google/gemma-2b-it"><code>google/gemma-2b-it</code></a></li>
+          <li><a href="https://huggingface.co/google/gemma-7b-it"><code>google/gemma-7b-it</code></a></li>
         </ul>
       </td>
     </tr>