chore(bitbucket): add note to issue management section

Author: ameliahsu

docs/organization/integrations/source-code-mgmt/bitbucket/index.mdx

@@ -146,6 +146,12 @@ For more details, see the full documentation on [commit tracking and releases](/
 
 ### Issue Management
 
+<Note>
+
+This feature is only supported on legacy Bitbucket instances. See [Bitbucket Support](https://support.atlassian.com/bitbucket-cloud/docs/use-the-issue-tracker/) for more details.
+
+</Note>
+
 Issue tracking allows you to create Bitbucket issues from within Sentry, and link Sentry issues to existing Bitbucket Issues.
 
 Once you’ve navigated to a specific issue, you’ll find the **Linked Issues** section on the right hand panel. Here, you’ll be able to create or link Bitbucket issues.