JS: don't remove imports only used for fake overrides (KT-31007 fixed)

js/js.translator/testData/box/multiModule/privateInterfaceMethodInheritance.kt

@@ -0,0 +1,25 @@
+// EXPECTED_REACHABLE_NODES: 1280
+// IGNORE_BACKEND: JS_IR
+// MODULE: lib
+// FILE: lib.kt
+package lib
+
+interface A {
+    private fun foo() = "OK"
+
+    fun bar() = foo()
+}
+
+open class AProxy: A
+
+// MODULE: main(lib)
+// FILE: main.kt
+package main
+
+// KT-31007
+import lib.AProxy
+
+// Important bit: don't inherit A directly
+class B : AProxy()
+
+fun box(): String = B().bar()