[SPARK-28962][SQL][FOLLOW-UP] Add the parameter description for the Scala function API filter

### What changes were proposed in this pull request?
This PR is a follow-up PR #25666 for adding the description and example for the Scala function API `filter`.

### Why are the changes needed?
It is hard to tell which parameter is the index column.

### Does this PR introduce any user-facing change?
No

### How was this patch tested?
N/A

Closes #27336 from gatorsmile/spark28962.

Authored-by: Xiao Li <gatorsmile@gmail.com>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

Author: gatorsmile

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

@@ -3455,6 +3455,13 @@ object functions {
 
   /**
    * Returns an array of elements for which a predicate holds in a given array.
+   * {{{
+   *   df.select(filter(col("s"), x => x % 2 === 0))
+   *   df.selectExpr("filter(col, x -> x % 2 == 0)")
+   * }}}
+   *
+   * @param column: the input array column
+   * @param f: col => predicate, the boolean predicate to filter the input column
    *
    * @group collection_funcs
    * @since 3.0.0
@@ -3465,6 +3472,14 @@ object functions {
 
   /**
    * Returns an array of elements for which a predicate holds in a given array.
+   * {{{
+   *   df.select(filter(col("s"), (x, i) => i % 2 === 0))
+   *   df.selectExpr("filter(col, (x, i) -> i % 2 == 0)")
+   * }}}
+   *
+   * @param column: the input array column
+   * @param f: (col, index) => predicate, the boolean predicate to filter the input column
+   *           given the index. Indices start at 0.
    *
    * @group collection_funcs
    * @since 3.0.0