Bump sqlalchemy from 1.3.15 to 1.3.16 (#944)

Bumps [sqlalchemy](https://github.com/sqlalchemy/sqlalchemy) from 1.3.15 to 1.3.16.
- [Release notes](https://github.com/sqlalchemy/sqlalchemy/releases)
- [Changelog](https://github.com/sqlalchemy/sqlalchemy/blob/master/CHANGES)
- [Commits](https://github.com/sqlalchemy/sqlalchemy/commits)

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requirements.txt

@@ -11,7 +11,7 @@ pytz>=2018.9
 whatthepatch>=0.0.5
 icalevents==0.1.25
 icalendar==4.0.5
-sqlalchemy==1.3.15
+sqlalchemy==1.3.16
 filelock==3.0.12
 alembic==1.4.2
 numpy==1.18.4