Migration to expect/actual: fix multiplatform integration tests

compiler/testData/multiplatform/genericDeclarations/common.kt

@@ -1,13 +1,13 @@
-header fun <T> f1(): T
+expect fun <T> f1(): T
 
-header fun <T> f2(t: T)
+expect fun <T> f2(t: T)
 
-header fun <K : Enum<K>, V : MutableList<out K>> f3(v: Map<V, Enum<in K>>, w: Comparable<*>)
+expect fun <K : Enum<K>, V : MutableList<out K>> f3(v: Map<V, Enum<in K>>, w: Comparable<*>)
 
-header fun <T: Comparable<T>> Array<out T>.sort(): Unit
+expect fun <T: Comparable<T>> Array<out T>.sort(): Unit
 
-header class C1<A>
-header class C2<B : C2<B>>
-header class C3<D, E : MutableList<in D>>
+expect class C1<A>
+expect class C2<B : C2<B>>
+expect class C3<D, E : MutableList<in D>>
 
-header abstract class AbstractList<F> : MutableList<F>
+expect abstract class AbstractList<F> : MutableList<F>