Update Documentation: leftsemi instead of semijoin

should sync up with here?
https://github.com/apache/spark/blob/119f45d61d7b48d376cca05e1b4f0c7fcf65bfa8/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/joinTypes.scala#L26

Author: LCY Vincent <lauchunyin@gmail.com>

Closes #5944 from vincentlaucy/master and squashes the following commits:

fc0e454 [LCY Vincent] Update DataFrame.scala

sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala

@@ -433,7 +433,7 @@ class DataFrame private[sql](
    *
    * @param right Right side of the join.
    * @param joinExprs Join expression.
-   * @param joinType One of: `inner`, `outer`, `left_outer`, `right_outer`, `semijoin`.
+   * @param joinType One of: `inner`, `outer`, `left_outer`, `right_outer`, `leftsemi`.
    * @group dfops
    */
   def join(right: DataFrame, joinExprs: Column, joinType: String): DataFrame = {