Bump flask from 1.1.2 to 2.0.1 in /main-webserver

Bumps [flask](https://github.com/pallets/flask) from 1.1.2 to 2.0.1.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/main/CHANGES.rst)
- [Commits](pallets/flask@1.1.2...2.0.1)

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

main-webserver/requirements.txt

@@ -4,7 +4,7 @@ boto3==1.17.22
 celery==5.1.0
 click==7.1.2
 cryptography==3.4.7
-Flask==1.1.2
+Flask==2.0.1
 Flask-Cors==3.0.10
 Flask-JWT-Extended==4.2.1
 Flask-Limiter==1.4