[hotfix][docs] Fix html tags in Batch API overview

docs/dev/batch/index.md

@@ -592,7 +592,7 @@ val output: DataSet[(Int, String, Double)] = input.sum(0).min(2)
   </td>
  </tr>
 
- </tr>
+ <tr>
   <td><strong>Join</strong></td>
   <td>
   Joins two data sets by creating all pairs of elements that are equal on their keys.
@@ -608,7 +608,7 @@ val result = input1.join(input2).where(0).equalTo(1)
  describe whether the join happens through partitioning or broadcasting, and whether it uses
  a sort-based or a hash-based algorithm. Please refer to the
  <a href="dataset_transformations.html#join-algorithm-hints">Transformations Guide</a> for
- a list of possible hints and an example.</br>
+ a list of possible hints and an example.<br />
  If no hint is specified, the system will try to make an estimate of the input sizes and
  pick the best strategy according to those estimates.
 {% highlight scala %}
@@ -700,7 +700,6 @@ val result = in.partitionByRange(0).mapPartition { ... }
 {% endhighlight %}
  </td>
  </tr>
- </tr>
  <tr>
  <td><strong>Custom Partitioning</strong></td>
  <td>