Update ISSUE_TEMPLATE.md (#16987)

Automatic Merge

.github/ISSUE_TEMPLATE.md

@@ -5,7 +5,7 @@ For feature proposals see: http://www.mattermost.org/feature-requests/
 
 If you've found a bug--something appears unintentional--please follow these steps:
 
-1. Confirm you’re filing a new issue. [Search existing tickets in Jira](https://mattermost.atlassian.net/issues/) to ensure that the ticket does not already exist.
+1. Confirm you’re filing a new issue. [Search existing tickets in Jira](https://mattermost.atlassian.net/jira/software/c/projects/MM/issues/) to ensure that the ticket does not already exist.
 2. Confirm your issue does not involve security. Otherwise, please see our [Responsible Disclosure Policy](https://about.mattermost.com/report-security-issue/).
 3. [File a new issue](https://github.com/mattermost/mattermost-server/issues/new) using the format below. Mattermost will confirm steps to reproduce and file in Jira, or ask for more details if there is trouble reproducing it. If there's already an existing bug in Jira, it will be linked back to the GitHub issue so you can track when it gets fixed.