Bump sqlalchemy from 1.3.8 to 1.3.9

Bumps [sqlalchemy](https://github.com/sqlalchemy/sqlalchemy) from 1.3.8 to 1.3.9.
- [Release notes](https://github.com/sqlalchemy/sqlalchemy/releases)
- [Changelog](https://github.com/sqlalchemy/sqlalchemy/blob/master/CHANGES)
- [Commits](https://github.com/sqlalchemy/sqlalchemy/commits)

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

requirements.txt

@@ -46,7 +46,7 @@ pyopenssl==19.0.0
 pyproj>=1.9.5,<2.2.3.0
 OWSLib==0.18.0
 pycsw==2.4.0
-SQLAlchemy==1.3.8 # required by PyCSW
+SQLAlchemy==1.3.9 # required by PyCSW
 Shapely==1.6.4.post2
 mercantile==1.1.2
 geoip2==2.9.0