[SPARK-21925] Update trigger interval documentation in docs with behavior change in Spark 2.2

Forgot to update docs with behavior change.

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #19138 from brkyvz/trigger-doc-fix.

docs/structured-streaming-programming-guide.md

@@ -1168,7 +1168,7 @@ returned through `Dataset.writeStream()`. You will have to specify one or more o
 
 - *Query name:* Optionally, specify a unique name of the query for identification.
 
-- *Trigger interval:* Optionally, specify the trigger interval. If it is not specified, the system will check for availability of new data as soon as the previous processing has completed. If a trigger time is missed because the previous processing has not completed, then the system will attempt to trigger at the next trigger point, not immediately after the processing has completed.
+- *Trigger interval:* Optionally, specify the trigger interval. If it is not specified, the system will check for availability of new data as soon as the previous processing has completed. If a trigger time is missed because the previous processing has not completed, then the system will trigger processing immediately.
 
 - *Checkpoint location:* For some output sinks where the end-to-end fault-tolerance can be guaranteed, specify the location where the system will write all the checkpoint information. This should be a directory in an HDFS-compatible fault-tolerant file system. The semantics of checkpointing is discussed in more detail in the next section.