Update 10min.rst
Added Links for Matplotlib Close along with a line explaining what it does.
I had faced difficulty when I read it for the first time and had to google search what close does

- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
