Make i21215 a pos test

Author: EugeneFlesselle

tests/neg/i21215.scala renamed to tests/pos/i21215.scala

@@ -9,6 +9,7 @@ trait Temporal[F[_]] extends MonadError[F, Throwable]
 
 trait FlatMapOps[F[_], A]:
   def flatMap[B](f: A => F[B]): F[B] = ???
+  def map[B](f: A => B): F[B] = ???
   def ifM[B](ifTrue: => F[B], ifFalse: => F[B])(implicit F: FlatMap[F]): F[B] = ???
 
 implicit def toFlatMapOps[F[_], A](target: F[A])(implicit tc: FlatMap[F]): FlatMapOps[F, A] = ???