We need to remove the sep_benchmarks task from the merge queue, keeping it only on PRs.

Longer story:

> The github_pr_number expansion is currently unavailable during github_merge_queue tasks, causing failures in scripts that rely on fetching PR metadata—specifically for identifying performance threshold override comments—during the merge process. Investigation determined that populating this expansion is technically infeasible because the GitHub Merge Queue combines changes from multiple PRs into a single merge group , preventing the necessary 1:1 mapping between the running patch and a unique PR number. Consequently, the documentation has been updated to reflect this limitation, and the current workaround involves manually adjusting thresholds to bypass the check until a long-term solution is implemented.