test: update certificate rejection message

Author: carlosmn

test/online/fetch_test.rb

@@ -54,7 +54,7 @@ def test_fetch_over_https_with_certificate_callback_fail
         })
       end
 
-      assert_equal "user cancelled certificate check", exception.message
+      assert_equal "user rejected certificate for github.com", exception.message
     end
 
     def test_fetch_over_https_with_certificate_callback_exception