docs: fix EVisRAG setup dir, TOC typo, and command continuation in README

[lingmao233]

What

Three small README fixes:

1. EVisRAG setup step is broken: after git clone https://github.com/OpenBMB/VisRAG.git the working directory is VisRAG, but the instructions say cd EVisRAG, which fails with no such file or directory. Changed to cd VisRAG. (The conda env is still created and activated as EVisRAG — only the directory name was wrong.)
2. TOC typo: "📄 Lisense" → "📄 License" (the anchor already pointed at the correct #-license heading).
3. Command continuation: removed a trailing whitespace after the line-continuation backslash in the generate.py example (--rank <process_rank> \ ), which breaks the continuation when the block is pasted into bash.

How I verified

• Checked the directory produced by the clone command (VisRAG) against the cd step; the conda env name is unaffected since only the cd target changed.
• Confirmed the TOC anchor #-license still matches the # 📄 License heading.
• Confirmed the trailing whitespace at byte level and removed it so the command block continues cleanly.