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

compiler/testData/diagnostics/tests/smartCasts/safecalls/falseExtension.fir.kt

@@ -0,0 +1,7 @@
+fun String.foo(y: Int) = y
+
+fun calc(x: List<String>?): Int {
+    "abc".foo(x!!.size)
+    // Here we should have smart cast because of x!!, despite of KT-7204 fixed
+    return x.size
+}