Filter out overridden candidates before looking for most specific

This filtering will remove signature duplicates that prevent findMaximallySpecific() from finding best candidate.

compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java

@@ -8388,6 +8388,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("varargConflict.kt")
+            public void testVarargConflict() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multimodule/varargConflict.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("compiler/testData/diagnostics/tests/multimodule/duplicateClass")
             @TestDataPath("$PROJECT_ROOT")
             @RunWith(JUnit3RunnerWithInners.class)