Outer's superclass' method is now inaccessible from nested

Also the diagnostic error message reported the wrong nested class name: it
should be the nested class in the hierarchy which is static, not the class of
the scope where we're checking the accessibility

idea/testData/diagnosticMessage/inaccessibleOuterClassExpression1.txt

@@ -0,0 +1,2 @@
+<!-- inaccessibleOuterClassExpression1 -->
+Expression is inaccessible from a nested class 'B', use 'inner' keyword to make the class inner