K2: add test for already fixed missing diagnostic issue

#KT-55956

compiler/testData/diagnostics/tests/regressions/kt55956.kt

@@ -0,0 +1,22 @@
+// FIR_IDENTICAL
+// TARGET_BACKEND: JVM_IR
+
+<!WRONG_ANNOTATION_TARGET_WITH_USE_SITE_TARGET!>@file:MyExperimentalAPI<!>
+
+@RequiresOptIn
+@Target(AnnotationTarget.CLASS)
+annotation class MyExperimentalAPI
+
+@MyExperimentalAPI
+class Some {
+    fun foo() {}
+}
+
+class Bar {
+    @OptIn(MyExperimentalAPI::class)
+    fun bar() {
+        Some().foo()
+    }
+}
+
+fun main(args: Array<String>) {}