Allow open callable members in expect interfaces

#KT-42094 fixed

compiler/testData/diagnostics/tests/modifiers/openInExpectInterface.fir.kt

@@ -0,0 +1,37 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+// TODO: .fir.kt version is just a stub.
+
+expect interface My {
+    open fun bar()
+    open fun bas() {}
+    <!REDUNDANT_MODIFIER!>open<!> abstract fun bat(): Int
+
+    fun foo()
+
+
+    open val a: Int
+    open val b: String
+    open val c: String get() = ""
+    <!REDUNDANT_MODIFIER!>open<!> abstract val e: Int
+
+    val f: Int
+}
+
+class MyImpl1: My
+
+class MyImpl2: My {
+    override fun foo() {}
+    override val f = 0
+    override val e = 1
+}
+
+expect interface Outer {
+    interface Inner {
+        open fun bar()
+        open fun bas() {}
+        <!REDUNDANT_MODIFIER!>open<!> abstract fun bat(): Int
+        fun foo()
+    }
+}