revert: remove ELO rank feature (data source inaccessible)

stat-check.com's ELO data is behind Microsoft auth with no public
API or download endpoint available. Removing the sync script,
placeholder JSON, CI job, table column, and all related JS.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

index.html

@@ -76,7 +76,6 @@
               <th class="text-right hidden sm:table-cell cursor-pointer select-none" data-sort="wlt">W–L–T</th>
               <th class="text-right hidden sm:table-cell cursor-pointer select-none" data-sort="wpct">Win %</th>
               <th class="text-right hidden sm:table-cell cursor-pointer select-none" data-sort="rank">ITC Rank</th>
-              <th class="text-right hidden sm:table-cell cursor-pointer select-none" data-sort="elo">ELO Rank</th>
             </tr>
           </thead>
           <tbody id="rows"></tbody>