fix: Remove assignees from weekly-docs-check workflow (#6375)

## Summary

Removes the `assignees` field from the weekly-docs-check workflow that
was causing failures.

## Problem

The workflow was attempting to assign `${{ github.repository_owner }}`
to created PRs. For organization-owned repositories,
`github.repository_owner` is the organization name (e.g., "Comfy-Org"),
which cannot be assigned to pull requests. Only individual GitHub users
can be assigned.

This was causing the workflow to fail:
https://github.com/Comfy-Org/ComfyUI_frontend/actions/runs/18901589988

## Solution

Removed the `assignees` line from the workflow configuration. The PRs
will still be created successfully, just without auto-assignment.

## Changes Made

- Removed `assignees: ${{ github.repository_owner }}` from
`.github/workflows/weekly-docs-check.yaml:145`

Fixes #6364

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6375-fix-Remove-assignees-from-weekly-docs-check-workflow-29b6d73d365081769ec2dc3e68005cc7)
by [Unito](https://www.unito.io)

Author: snomiao

.github/workflows/weekly-docs-check.yaml

@@ -142,4 +142,3 @@ jobs:
             documentation
             automated
           draft: true
-          assignees: ${{ github.repository_owner }}