Bump idna from 2.6 to 2.8

Bumps [idna](https://github.com/kjd/idna) from 2.6 to 2.8.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.rst)
- [Commits](kjd/idna@v2.6...v2.8)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

requirements.txt

@@ -16,7 +16,7 @@ Flask-Moment==0.5.2
 Flask-SQLAlchemy==2.4.0
 Flask-WTF==0.14.2
 guess_language-spirit==0.5.3
-idna==2.6
+idna==2.8
 itsdangerous==0.24
 Jinja2==2.10.1
 Mako==1.1.0