Migration to expect/actual: fix multiplatform highlighting tests

idea/testData/multiModuleHighlighting/multiplatform/headerFunctionProperty/common/common.kt

@@ -1,3 +1,3 @@
-header fun foo(): Int
+expect fun foo(): Int
 
-header val bar: String
+expect val bar: String

idea/testData/multiModuleHighlighting/multiplatform/headerFunctionProperty/jvm/jvm.kt

@@ -1,3 +1,3 @@
-impl fun foo() = 42
+actual fun foo() = 42
 
-impl val bar = "Hello"
+actual val bar = "Hello"