documentation: Update "Ask a question" contact link (#2348)

Author: bveeramani

.github/ISSUE_TEMPLATE/config.yml

@@ -1,5 +1,5 @@
 blank_issues_enabled: false
 contact_links:
   - name: Ask a question
-    url: https://stackoverflow.com/questions/tagged/amazon-sagemaker
-    about: Use Stack Overflow to ask and answer questions
+    url: https://github.com/aws/sagemaker-python-sdk/discussions
+    about: Use GitHub Discussions to ask and answer questions