don't erase method invocation type iff unchecked conversion was required during additional constraints processing (IDEA-163503)

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/graphInference/ErasureOfReturnTypeIffUncheckedConversionWasNecessaryDuringApplicabilityCheckOnly.java

@@ -0,0 +1,8 @@
+import java.util.List;
+import java.util.stream.Collectors;
+
+class Test {
+  private static List<Object> test(List<List> list) {
+    return list.stream().flatMap(List::stream).collect(Collectors.toList());
+  }
+}