Bump jinja2 from 2.11.1 to 3.1.3 in /example

Bumps [jinja2](https://github.com/pallets/jinja) from 2.11.1 to 3.1.3.
- [Release notes](https://github.com/pallets/jinja/releases)
- [Changelog](https://github.com/pallets/jinja/blob/main/CHANGES.rst)
- [Commits](pallets/jinja@2.11.1...3.1.3)

---
updated-dependencies:
- dependency-name: jinja2
  dependency-type: direct:production
...

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

example/requirements.txt

@@ -9,7 +9,7 @@ Flask-MQTT==1.0.5
 Flask-SocketIO==3.3.2
 greenlet==0.4.15
 itsdangerous==1.1.0
-Jinja2==2.11.1
+Jinja2==3.1.3
 MarkupSafe==1.1.1
 monotonic==1.5
 paho-mqtt==1.5.0