chore: update feature request template (#6614)

Author: bombsimon

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -8,6 +8,8 @@ body:
     attributes:
       label: Welcome
       options:
+        - label: This is not a request to create or integrate a new linter; those belong in [Discussions](https://github.com/golangci/golangci-lint/discussions/new/choose).
+          required: true
         - label: Yes, I've searched similar [issues on GitHub](https://github.com/golangci/golangci-lint/issues) and didn't find any.
           required: true
         - label: I agree to follow this project's [Code of Conduct](https://github.com/golangci/golangci-lint?tab=coc-ov-file)