[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/dataFlow/CalleeExpression.fir.kt

@@ -0,0 +1,7 @@
+class C(val f : () -> Unit)
+
+fun test(e : Any) {
+    if (e is C) {
+        (e.f)()
+    }
+}