[FIR] Update testdata according to KT-45223

compiler/testData/diagnostics/tests/j+k/collectionOverrides/overridesBuiltinNoMagic.fir.kt

@@ -150,14 +150,14 @@ class Y2 : X() {
 
 fun main() {
     X().remove("")
-    X().removeAt(1)
+    X().<!AMBIGUITY!>removeAt<!>(1)
 
     val y: MutableList<String> = Y()
     y.removeAt(1)
 
     Y().remove("")
-    Y().removeAt(1)
+    Y().<!AMBIGUITY!>removeAt<!>(1)
 
     X().remove("")
-    X().removeAt(1)
+    X().<!AMBIGUITY!>removeAt<!>(1)
 }

compiler/testData/diagnostics/tests/j+k/collectionOverrides/removeAtInt.fir.kt

@@ -0,0 +1,32 @@
+// JAVAC_EXPECTED_FILE
+// FILE: A.java
+abstract public class A extends B {
+    public Integer removeAt(int x) { }
+    public boolean remove(Integer x) { }
+}
+
+// FILE: main.kt
+import java.util.*;
+
+abstract class B : MutableList<Int>, AbstractList<Int>() {
+    override fun removeAt(index: Int): Int = null!!
+    override fun remove(element: Int): Boolean = null!!
+}
+
+abstract class D : AbstractList<Int>() {
+    // removeAt() doesn't exist in java/util/AbstractList, it's a
+    // fake override of the method from kotlin/collections/MutableList
+    override fun removeAt(index: Int): Int = null!!
+    // AbstractList::remove() should return Int here. No fake overrides created.
+    // This may be a bug because the old compiler doesn't report a diagnostic here.
+    override fun remove(element: Int): Boolean = null!!
+}
+
+fun main(a: A, b: B, c: ArrayList<Int>) {
+    a.remove(1)
+    a.<!AMBIGUITY!>removeAt<!>(0)
+    b.remove(1)
+    b.removeAt(0)
+    c.remove(1)
+    c.removeAt(0)
+}

compiler/testData/diagnostics/tests/j+k/collectionOverrides/removeAtInt.kt

@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 // JAVAC_EXPECTED_FILE
 // FILE: A.java
 abstract public class A extends B {