Fix spelling and grammar in multi_input_tool.ipynb (#2337)
Changes:
- Corrected the title to use hyphens instead of spaces.
- Fixed a typo in the second paragraph where "therefor" was changed to
"Therefore".
- Added a hyphen between "comma" and "separated" in the last paragraph.
File link:
[multi_input_tool.ipynb](https://github.com/hwchase17/langchain/blob/master/docs/modules/agents/tools/multi_input_tool.ipynb)
