Migration to expect/actual: fix multiplatform integration tests

compiler/testData/multiplatform/createImplClassInPlatformModule/common.kt

@@ -1 +1 @@
-header class Foo
+expect class Foo

compiler/testData/multiplatform/createImplClassInPlatformModule/jvm.kt

@@ -1,5 +1,5 @@
-impl class Foo(x: Int) {
-    impl constructor() : this(0)
+actual class Foo(x: Int) {
+    actual constructor() : this(0)
 
     val x: Int = x
 }