## What changes were proposed in this pull request?
I suspect that the doc of `rowsBetween` methods in Scala and PySpark looks wrong.
Because:
```scala
scala> val df = Seq((1, "a"), (2, "a"), (3, "a"), (4, "a"), (5, "a"), (6, "a")).toDF("id", "category")
df: org.apache.spark.sql.DataFrame = [id: int, category: string]
scala> val byCategoryOrderedById = Window.partitionBy('category).orderBy('id).rowsBetween(-1, 2)
byCategoryOrderedById: org.apache.spark.sql.expressions.WindowSpec = org.apache.spark.sql.expressions.WindowSpec7f04de97
scala> df.withColumn("sum", sum('id) over byCategoryOrderedById).show()
+---+--------+---+
| id|category|sum|
+---+--------+---+
| 1| a| 6| # sum from index 0 to (0 + 2): 1 + 2 + 3 = 6
| 2| a| 10| # sum from index (1 - 1) to (1 + 2): 1 + 2 + 3 + 4 = 10
| 3| a| 14|
| 4| a| 18|
| 5| a| 15|
| 6| a| 11|
+---+--------+---+
```
So the frame (-1, 2) for row with index 5, as described in the doc, should range from index 4 to index 7.
## How was this patch tested?
N/A, just doc change.
Closes#24864 from viirya/window-spec-doc.
Authored-by: Liang-Chi Hsieh <viirya@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
c0297dedd8