[FLINK-18591][metrics][documentation] Fix the format issue for metric…

…s web page

docs/monitoring/metrics.md

@@ -1290,7 +1290,7 @@ Metrics related to data exchange between task executors using netty network comm
   </thead>
   <tbody>
     <tr>
-      <th rowspan="9"><strong>Job (only available on JobManager)</strong></th>
+      <th rowspan="8"><strong>Job (only available on JobManager)</strong></th>
       <td>lastCheckpointDuration</td>
       <td>The time it took to complete the last checkpoint (in milliseconds).</td>
       <td>Gauge</td>
@@ -1331,7 +1331,7 @@ Metrics related to data exchange between task executors using netty network comm
       <td>Gauge</td>
     </tr>
     <tr>
-      <th rowspan="2">Task</th>
+      <th rowspan="2"><strong>Task</strong></th>
       <td>checkpointAlignmentTime</td>
       <td>The time in nanoseconds that the last barrier alignment took to complete, or how long the current alignment has taken so far (in nanoseconds).</td>
       <td>Gauge</td>
@@ -1365,7 +1365,7 @@ Certain RocksDB native metrics are available but disabled by default, you can fi
       <td>Histogram</td>
     </tr>
     <tr>
-      <th rowspan="13"><strong>Task</strong></th>
+      <th rowspan="14"><strong>Task</strong></th>
       <td>numBytesInLocal</td>
       <td><span class="label label-danger">Attention:</span> deprecated, use <a href="{{ site.baseurl }}/monitoring/metrics.html#default-shuffle-service">Default shuffle service metrics</a>.</td>
       <td>Counter</td>