FIR checker: warn unnecessary non-null assertions

compiler/testData/diagnostics/tests/resolve/invoke/kt4204-completeNestedCallsForInvoke.fir.kt

@@ -1,24 +0,0 @@
-//KT-4204 ConstraintSystem erased after resolution completion
-package c
-
-public abstract class TestBug1() {
-
-    public fun m3(position: Int) {
-        position(m1().second!!)
-    }
-
-    public fun m4(position: (Int)->Int) {
-        position(m1().second)
-    }
-
-    <!INCOMPATIBLE_MODIFIERS!>private<!> <!INCOMPATIBLE_MODIFIERS!>abstract<!> fun m1(): Pair<Int, Int>
-
-    private fun position(p: Int) {}
-
-}
-
-//from library
-public class Pair<out A, out B> (
-    public val first: A,
-    public val second: B
-)

compiler/testData/diagnostics/tests/resolve/invoke/kt4204-completeNestedCallsForInvoke.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 //KT-4204 ConstraintSystem erased after resolution completion
 package c