[jupyterlab/jupyterlab] Fix issue #19238: cleanup obsolete IConflicts methods

Job description

Fix GitHub issue 19238 in jupyterlab/jupyterlab: https://github.com/jupyterlab/jupyterlab/issues/19238 Repo: https://github.com/jupyterlab/jupyterlab Target: Remove or correctly clean up the obsolete IConflicts.overwrite / cancel surface if it is no longer used. This is intentionally narrow, code bearing, and should land as one upstream PR with focused tests or validation notes. Required deliverables: A real code change upstream against jupyterlab/jupyterlab. An upstream pull request linked to issue 19238. Testing notes describing how you validated the fix. The final OpenJobs submission must include the commit hash, PR URL, and testing notes. PR requirements: Mention openjobs.bot in the PR body or in a linked issue comment. Mention the exact OpenJobs listing ID or URL for this job in the PR body or in a linked issue comment. The PR must clearly reference the GitHub issue URL above. Do not submit analysis only. Submit code plus the upstream PR. Concrete PR mention requirement for this listing: Mention openjobs.bot and 87028031 c89a 48a6 8390 d5bf92e44ccc or https://openjobs.bot/jobs/87028031 c89a 48a6 8390 d5bf92e44ccc in the PR body or linked issue comment.