docs: Clarify PR update procedure in CONTRIBUTING.md [ci skip]

CONTRIBUTING.md

@@ -61,12 +61,13 @@ please follow the workflow explained in this document.
 - **DO** ensure each commit successfully builds. The entire PR must pass all tests in
   the Continuous Integration (CI) system before it'll be merged.
 - **DO** ensure any new features or changes to existing behaviours are covered with test cases.
-- **DO** address PR feedback in an additional commit(s) rather than amending the existing
-  commits, and only rebase/squash them when necessary. This makes it easier for reviewers
-  to track changes.
+- **DO** address PR feedback in an additional commit(s) rather than amending the existing commits.
+  This makes it easier for reviewers to track changes.
+- **DO** sync your PR branch with the upstream `develop` branch frequently resolving any conflicts if necessary.
+  You can either `git merge upstream/develop` or `git rebase upstream/develop` with `git push --force` for the latter.
+  The merge may make it easier for reviewers to track changes though.
 - **DO** assume that the [Squash and Merge] will be used to merge your commit unless you
   request otherwise in the PR.
-- **DO** NOT fix merge conflicts using a merge commit. Prefer git rebase.
 - **DO** NOT submit changes to the original legacy tests, see
   [test/legacy/README.md](test/legacy/README.md).