[STREAMING][MINOR] Fix a duplicate "be" in comments

Author: Liwei Lin <proflin.me@gmail.com>

Closes #11650 from lw-lin/typo.

streaming/src/main/scala/org/apache/spark/streaming/StateSpec.scala

@@ -83,8 +83,7 @@ sealed abstract class StateSpec[KeyType, ValueType, StateType, MappedType] exten
   def numPartitions(numPartitions: Int): this.type
 
   /**
-   * Set the partitioner by which the state RDDs generated by `mapWithState` will be
-   * be partitioned.
+   * Set the partitioner by which the state RDDs generated by `mapWithState` will be partitioned.
    */
   def partitioner(partitioner: Partitioner): this.type