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

compiler/testData/diagnostics/tests/smartCasts/varInSecondaryConstructor.fir.kt

@@ -0,0 +1,10 @@
+class My(val z: Int) {
+    var x: Int = 0
+    constructor(arg: Int?): this(arg ?: 42) {
+        var y: Int?
+        y = arg
+        if (y != null) {
+            x = y
+        }
+    }
+}