Bump idna from 3.0 to 3.1

Bumps [idna](https://github.com/kjd/idna) from 3.0 to 3.1.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.rst)
- [Commits](kjd/idna@v3.0...v3.1)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -12,7 +12,7 @@ attrs==20.3.0             # via aiohttp
 cffi==1.14.4              # via pycares
 chardet==3.0.4            # via aiohttp
 fonttools==4.18.2         # via fdiff (setup.py)
-idna==3.0                # via yarl
+idna==3.1                # via yarl
 multidict==5.1.0          # via aiohttp, yarl
 pycares==3.1.1            # via aiodns
 pycparser==2.20           # via cffi