fix generate code indent. prepare Scala 3

Author: xuwei-k

core/shared/src/main/boilerplate/kantan/csv/GeneratedRowEncoders.scala.template

@@ -108,7 +108,8 @@ trait GeneratedRowEncoders {
     *
     * @param f encoding method, intended to be a case class' `unapply` method.
     * @param i1 index of the cell that should be passed as parameter number 1 of `f`#
-    */  def caseEncoder[C, A1: CellEncoder](f: C => Option[A1]): RowEncoder[C] =
+    */
+  def caseEncoder[C, A1: CellEncoder](f: C => Option[A1]): RowEncoder[C] =
     encoder(f andThen (_.get))
 
   [2..#/** Creates a new [[RowEncoder]] from the specified `unapply` method of a case class' companion object.

core/shared/src/main/boilerplate/kantan/csv/TupleInstances.scala.template

@@ -26,7 +26,7 @@ trait TupleInstances {
     * res0: DecodeResult[Tuple1[[#Int#]]] = Right(([#1#,]))
     * }}}
     */
-   implicit def tupleRowDecoder1[[#A1: CellDecoder#]]: RowDecoder[Tuple1[[#A1#]]] =
+  implicit def tupleRowDecoder1[[#A1: CellDecoder#]]: RowDecoder[Tuple1[[#A1#]]] =
     RowDecoder.ordered(Tuple1.apply[[#A1#]] _)#
 
   ]
@@ -49,7 +49,8 @@ trait TupleInstances {
     * scala> RowEncoder[Tuple1[[#Int#]]].encode(([#1#]))
     * res0: Seq[String] = Vector([#1#])
     * }}}
-    */implicit def tupleRowEncoder1[[#A1: CellEncoder#]]: RowEncoder[Tuple1[[#A1#]]] =
+    */
+  implicit def tupleRowEncoder1[[#A1: CellEncoder#]]: RowEncoder[Tuple1[[#A1#]]] =
     RowEncoder.ordered((t: Tuple1[[#A1#]]) => t)#
 
   ]