[calendar] Ignore running some tests by Yeti in Calendar tests (Fix #1363)

Currently, running Calendar tests containing the focus process will fail in Firefox. The cause of this problem seems to be a problem that test case is not bad, what happens if you are running Yeti while running Firefox in the background. This problem does not occur in a browser other than Firefox. In addition, there is a test that includes a focusing process in the same way with the Widget Button module ([src/widget-buttons/tests/unit/assets/widget-buttons-test.js](https://github.com/yui/yui3/blob/master/src/widget-buttons/tests/unit/assets/widget-buttons-test.js)), so it has to ignore Yeti is here. Therefore, I would like to ignore running some tests by Yeti in the same way in Calendar. Fix #1363.