Fix modules/zend.i18n.view.helper.plural.rst broken links

Fix broken links as seen in ```make linkcheck``` output:

>modules/zend.i18n.view.helper.plural.rst:27: [broken] http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/language_plural_rules.html](http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/language_plural_rules.html: HTTP Error 404: Not Found
modules/zend.i18n.view.helper.plural.rst:28: [broken] https://developer.mozilla.org/en-US/docs/Localization_and_Plurals](https://developer.mozilla.org/en-US/docs/Localization_and_Plurals: HTTP Error 404: NOT FOUND