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

compiler/testData/diagnostics/tests/smartCasts/inference/kt4403.fir.kt

@@ -0,0 +1,11 @@
+//KT-4403 Wrong "type mismatch" on smart cast with inference
+
+interface A
+interface B : A
+
+fun <T> T.f(): T = this
+
+fun test(a: A) {
+    if (a !is B) return
+    val c = a.f() // type mismatch
+}