Update Slack signup link in SUPPORT_QUESTION.md

Not sure if this is present in other repos, but I noticed the current URL is broken and found the new one :)

.github/ISSUE_TEMPLATE/SUPPORT_QUESTION.md

@@ -13,7 +13,7 @@ For usage and support questions, please check out the resources below. Thanks!
 
 You can get answers to your usage and support questions about **Apache Cordova** on:
 
-* Slack Community Chat: https://cordova.slack.com (you can sign-up at http://slack.cordova.io/)
+* Slack Community Chat: https://cordova.slack.com (you can sign-up at https://s.apache.org/cordova-slack)
 * StackOverflow: https://stackoverflow.com/questions/tagged/cordova using the tag `cordova`
 
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