FE: fix a typo in irrelevantMapGetAbstract.kt diagnostic test

Related to KT-45053

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

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // FILE: Dict.java
 
 public abstract class Dict<K, V> {
@@ -7,7 +8,7 @@ public abstract class Dict<K, V> {
 // FILE: MHashtable.java
 
 abstract public class MHashtable<X, Y> extends Dict<X, Y> implements java.util.Map<X, Y> {
-    public V get(Object key) { return null; }
+    public Y get(Object key) { return null; }
 }
 
 // FILE: main.kt