[MINOR] Fix some indent issues.

## What changes were proposed in this pull request?

Fix some indent issues.

## How was this patch tested?

existing tests.

Author: Yuming Wang <wgyumg@gmail.com>

Closes #18133 from wangyum/IndentIssues.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/hash.scala

@@ -524,7 +524,7 @@ abstract class InterpretedHashFunction {
   extended = """
     Examples:
       > SELECT _FUNC_('Spark', array(123), 2);
-        -1321691492
+       -1321691492
   """)
 case class Murmur3Hash(children: Seq[Expression], seed: Int) extends HashExpression[Int] {
   def this(arguments: Seq[Expression]) = this(arguments, 42)

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/nullExpressions.scala

@@ -116,9 +116,9 @@ case class IfNull(left: Expression, right: Expression, child: Expression)
 @ExpressionDescription(
   usage = "_FUNC_(expr1, expr2) - Returns null if `expr1` equals to `expr2`, or `expr1` otherwise.",
   extended = """
-   Examples:
+    Examples:
-     > SELECT _FUNC_(2, 2);
+      > SELECT _FUNC_(2, 2);
-      NULL
+       NULL
   """)
 case class NullIf(left: Expression, right: Expression, child: Expression)
   extends RuntimeReplaceable {

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala

@@ -99,7 +99,7 @@ abstract class StringRegexExpression extends BinaryExpression
 
     See also:
       Use RLIKE to match with standard regular expressions.
-""")
+  """)
 case class Like(left: Expression, right: Expression) extends StringRegexExpression {
 
   override def escape(v: String): String = StringUtils.escapeLikeRegex(v)
@@ -175,7 +175,7 @@ case class Like(left: Expression, right: Expression) extends StringRegexExpressi
 
     See also:
       Use LIKE to match with simple string pattern.
-""")
+  """)
 case class RLike(left: Expression, right: Expression) extends StringRegexExpression {
 
   override def escape(v: String): String = v

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala

@@ -770,10 +770,10 @@ case class StringLPad(str: Expression, len: Expression, pad: Expression)
   """,
   extended = """
     Examples:
-     > SELECT _FUNC_('hi', 5, '??');
+      > SELECT _FUNC_('hi', 5, '??');
-      hi???
+       hi???
-     > SELECT _FUNC_('hi', 1, '??');
+      > SELECT _FUNC_('hi', 1, '??');
-      h
+       h
   """)
 case class StringRPad(str: Expression, len: Expression, pad: Expression)
   extends TernaryExpression with ImplicitCastInputTypes {