Link to SBOM user documentation from release detail page (#2363)

Author: sethmlarson

templates/downloads/release_detail.html

@@ -55,7 +55,7 @@ <h1 class="page-title">Files</h1>
               <th colspan="2"><a href="https://www.python.org/download/sigstore/">Sigstore</a></th>
               {% endif %}
               {% if release_files|has_sbom %}
-              <th>SBOM</th>
+              <th><a href="https://www.python.org/download/sbom/">SBOM</a></th>
               {% endif %}
             </tr>
           </thead>