Bump jinja2 from 2.10.1 to 2.11.3 in /server

Bumps [jinja2](https://github.com/pallets/jinja) from 2.10.1 to 2.11.3.
- [Release notes](https://github.com/pallets/jinja/releases)
- [Changelog](https://github.com/pallets/jinja/blob/master/CHANGES.rst)
- [Commits](pallets/jinja@2.10.1...2.11.3)

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

server/requirements.txt

@@ -6,7 +6,7 @@ Flask-Cors==3.0.6
 gcm==0.3
 idna==2.7
 itsdangerous==0.24
-Jinja2==2.10.1
+Jinja2==2.11.3
 MarkupSafe==1.0
 nltk==3.4.5
 pyenchant==2.0.0