Do not suggest to add variance modifier if both in and out are possible

idea/testData/inspections/addVarianceModifier/inspectionData/expected.xml

@@ -31,12 +31,4 @@
         <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Type parameter can have 'in' or 'out' variance</problem_class>
         <description>Type parameter can have 'in' variance</description>
     </problem>
-    <problem>
-        <file>test.kt</file>
-        <line>24</line>
-        <module>light_idea_test_case</module>
-        <entry_point TYPE="file" FQNAME="temp:///src/test.kt" />
-        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Type parameter can have 'in' or 'out' variance</problem_class>
-        <description>Type parameter can have 'in' or 'out' variance</description>
-    </problem>
 </problems>

idea/testData/inspections/addVarianceModifier/test.kt

@@ -21,7 +21,7 @@ abstract class AbstractOut<T> {
 abstract class AbstractIn<T>(private val foo: T) {
     fun bar(arg: T) = foo == arg
 }
-interface Empty<T>
+interface Empty<T> // here we do not report anything to avoid ambiguity
 
 abstract class AbstractInv<T>(var foo: T)