Refactoring: move test folder out of "inline classes" folder

It was added there by mistake

compiler/testData/codegen/box/funInterface/basicFunInterfaceConversion.kt

@@ -0,0 +1,11 @@
+// !LANGUAGE: +NewInference +FunctionInterfaceConversion +SamConversionPerArgument +SamConversionForKotlinFunctions
+
+fun interface Foo {
+    fun invoke(): String
+}
+
+fun foo(f: Foo) = f.invoke()
+
+fun box(): String {
+    return foo { "OK" }
+}