Bump flask-sqlalchemy from 2.3.2 to 2.4.0 in /{{cookiecutter.app_name}}

Bumps [flask-sqlalchemy](https://github.com/pallets/flask-sqlalchemy) from 2.3.2 to 2.4.0.
- [Release notes](https://github.com/pallets/flask-sqlalchemy/releases)
- [Changelog](https://github.com/pallets/flask-sqlalchemy/blob/master/docs/changelog.rst)
- [Commits](https://github.com/pallets/flask-sqlalchemy/compare/2.3.2...2.4.0)

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

{{cookiecutter.app_name}}/Pipfile

@@ -13,7 +13,7 @@ itsdangerous = "==1.1.0"
 click = ">=5.0"
 
 # Database
-Flask-SQLAlchemy = "==2.3.2"
+Flask-SQLAlchemy = "==2.4.0"
 psycopg2 = "==2.8.2"
 SQLAlchemy = "==1.3.3"