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

compiler/testData/diagnostics/tests/smartCasts/inference/kt29767.fir.kt

@@ -0,0 +1,11 @@
+// !WITH_NEW_INFERENCE
+// ISSUE: KT-29767
+
+fun test(a: MutableList<out Int?>?) {
+    if (a != null) {
+        val b = a[0] // no SMARTCAST diagnostic
+        if (b != null) {
+            b.inc()
+        }
+    }
+}