Fixed loading variance from alternative signature.

compiler/testData/loadJava/kotlinSignature/CustomVariance.java

@@ -0,0 +1,12 @@
+package test;
+
+import java.util.*;
+
+import jet.runtime.typeinfo.KotlinSignature;
+
+public class CustomVariance {
+    @KotlinSignature("fun foo(): MutableList<out Number>")
+    public List<Number> foo() {
+        throw new UnsupportedOperationException();
+    }
+}