Update test affected by SafeCallsAreAlwaysNullable feature

compiler/testData/diagnostics/tests/SafeCallNonNullReceiver2.kt

@@ -0,0 +1,7 @@
+// FIR_IDENTICAL
+// http://youtrack.jetbrains.net/issue/KT-418
+
+fun ff() {
+    val i: Int = 1
+    val a: Int? = i<!UNNECESSARY_SAFE_CALL!>?.<!>plus(2)
+}