[FIR] Remove legacy annotation @VisitedSupertype

compiler/fir/tree/src/org/jetbrains/kotlin/fir/VisitedSupertype.kt

@@ -1,14 +0,0 @@
-/*
- * Copyright 2000-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.fir
-
-// This annotation is used in FIR interface super-type list
-// It *should* be used if super-type list includes more than one FIR element
-// It marks the single super-type to which visitor should proceed by default
-
-@Retention(AnnotationRetention.SOURCE)
-@Target(AnnotationTarget.TYPE)
-annotation class VisitedSupertype