Bump flask-migrate from 2.5.2 to 2.5.3

Bumps [flask-migrate](https://github.com/miguelgrinberg/flask-migrate) from 2.5.2 to 2.5.3.
- [Release notes](https://github.com/miguelgrinberg/flask-migrate/releases)
- [Changelog](https://github.com/miguelgrinberg/Flask-Migrate/blob/master/CHANGES.md)
- [Commits](https://github.com/miguelgrinberg/flask-migrate/compare/v2.5.2...v2.5.3)

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

setup.py

@@ -34,7 +34,7 @@ setup(
     install_requires=[
         'Flask==1.1.1',
         'Flask-SQLAlchemy==2.4.1',
-        'Flask-Migrate==2.5.2',
+        'Flask-Migrate==2.5.3',
         'Flask-Bootstrap==3.3.7.1',
         'Flask-WTF==0.14.3',
         'Flask-Caching==1.8.0',