chore: make the URL of the support forum more specific

Author: kenjis

.github/ISSUE_TEMPLATE/config.yml

@@ -1,7 +1,7 @@
 blank_issues_enabled: false
 contact_links:
   - name: CodeIgniter Forum
-    url: https://forum.codeigniter.com
+    url: https://forum.codeigniter.com/forum-30.html
     about: Please ask your support questions in the forums. Thanks!
 
   - name: CodeIgniter Slack channel