Fixed typo

## What changes were proposed in this pull request?

Fixed small typo - "value ... ~~in~~ is null"

## How was this patch tested?

Still compiles!

Author: Michał Kiełbowicz <jupblb@users.noreply.github.com>

Closes #14569 from jupblb/typo-fix.

sql/catalyst/src/main/scala/org/apache/spark/sql/Row.scala

@@ -463,6 +463,6 @@ trait Row extends Serializable {
    * @throws NullPointerException when value is null.
    */
   private def getAnyValAs[T <: AnyVal](i: Int): T =
-    if (isNullAt(i)) throw new NullPointerException(s"Value at index $i in null")
+    if (isNullAt(i)) throw new NullPointerException(s"Value at index $i is null")
     else getAs[T](i)
 }