[SPARK-23931][SQL][FOLLOW-UP] Make arrays_zip in function.scala @scala.annotation.varargs.

## What changes were proposed in this pull request?

This is a follow-up pr of apache#21045 which added `arrays_zip`.
The `arrays_zip` in functions.scala should've been `scala.annotation.varargs`.

This pr makes it `scala.annotation.varargs`.

## How was this patch tested?

Existing tests.

Author: Takuya UESHIN <[email protected]>

Closes apache#21630 from ueshin/issues/SPARK-23931/fup1.

Author: ueshin

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

@@ -3539,6 +3539,7 @@ object functions {
    * @group collection_funcs
    * @since 2.4.0
    */
+  @scala.annotation.varargs
   def arrays_zip(e: Column*): Column = withExpr { ArraysZip(e.map(_.expr)) }
 
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